NOTE: This is my new approach of reviewing games.
This is the final Mass Effect game that concludes Commander Shepard's storyline. It is one of the best games I have ever played, albeit some flaws that prevented it from being a true masterpiece.
Storyline
The storyline is nearly perfect. Great character interactions, good story pacing, interesting character developments, good plot twists, and well written. Unfortunately, the game's three main endings are not that good and not satisfying. The three main endings are abrupt, not well developed and not well explained. The endings did not explain properly what are the consequences after certain actions being done in this game as well as previous Mass Effect games. This is a truly disappointment to many Mass Effect fans, including me as well.
Gameplay
i) Importing section (Singleplayer)
For PS3 players, you do not have the luxury of playing the first Mass Effect game because it is a Microsoft exclusive game. The only way for you to carry over important decisions from the first Mass Effect game is to purchase and play Mass Effect: Genesis, an interactive comic that details significant events happened in the first game and allows you to choose important decisions to be carried over to Mass Effect 2 and Mass Effect 3. New copies of the PS3 version of Mass Effect 2 will have the free download code for Mass Effect: Genesis, but if you are playing the second hand copies of Mass Effect 2, you need to purchase it from PlayStation Store.
ii) Exploration, progression and customisation section (Singleplayer)
Exploration is similar to previous Mass Effect games, where you need to move your character from a location to another and talk to someone to progress in a Mission. While in the Normandy and the Citadel, you can move around and talk to people to initiate interesting and insightful conversations, or initiate side quests by talking to them.
The Galaxy Map is the same as the previous games, but now you have Reapers invading in certain Systems in the galaxy. You can scan planets for War Assets, but by doing so, Reapers will be alarmed to your presence and will try to catch and destroy you if you use scan the planets too many times. If they have caught up to you, you will get a Game Over, and you need to restart your most recent save again.
After finding planets that have War Assets, you can scan the planet and send a pod to retrieve it by following the pointer on your radar. It can be either Credits (in-game money), or War Assets that help you in the final battle against the Reapers.
War Assets have their own Effective Military Strength (EMS). By completing missions and side missions, you will obtain War Assets that will boost your EMS to fight the Reapers. Provided that you do not have enough EMS when you are fighting the Reapers in the final battle, the consequences might be fatal. It is best if you complete side missions to achieve the minimum EMS to fight the Reapers.
Each Missions have their own objectives, and you can only progress in the Mission by completing the require objectives. Some missions have Priority in the name, whereas some don't. By only completing the Priority missions that you are allowed to progress in the game. Completing missions that do not have Priority are optional, but it is best to complete them to obtain more War Assets.
Side quests are obtained by hearing NPCs talking aloud in the Citadel. Most of it require you to scan a planet, and retrieve something from there. It is quite boring to do so, but most of the side quests offer you some good rewards such as War Assets and Credits. The method of retrieving something from a planet is the toned down version of Mass Effect 2's mineral scanning.
The Morality system returns in the game, but it also features the Reputation system. Reputation acts as a multiplier to your Paragon and Renegade points, and you will get more Reputation points by completing Missions and Side Quests. The conversation system is the same as in previous games, where the conversation come in a form of dialogue wheel. You can inquire further information from a character in the game, or ask him/her to do something. Certain important decisions can only be done by choosing a Paragon option or Renegade option. You can only choose the Paragon or Renegade options only if your Paragon and Renegade points are high enough. You can also interrupt a conversation by doing a Paragon action or Renegade action. Doing so allows you to change the intended outcome of the conversation and also nets you more Paragon or Renegade points.
When you play a default new game, you can customise on how your Commander Shepard looks like, gender, class, and personal history. Some of these details may affect certain things in the game, such as your potential romance interests, your power sets, etc. If you import the completed save file from Mass Effect 2, all of those details will be carried over to this game.
Your Shepard's appearance can be changed, such as you can change his/her casual clothes, or customise armour parts for combat. Some armour parts may have different bonuses, such as slight health bonus, etc. So try experiment a bit with the armour parts. In addition to that, your armour will look different if you use a new and different parts. You can also purchase complete armour sets from the Stores, but they are quite costly, and you better spending off your Credits in buying other stuffs.
iii) Combat section (Singleplayer)
iv) Multiplayer section (Multiplayer)
The multiplayer does not feature competitive play with other players, but cooperative play with other players, meaning no friendly fire. In the online matches, you need to fights waves of enemies (Cerberus, Reapers, geth) in a map. There are 10 waves, but some waves require you to complete certain objectives, such as disabling a device, hacking a device. After surviving all 10 waves, you will need to go to an evacuation area, and you will need to wait until a time limit runs out to complete the match.
Killing an enemy rewards you XP points to level up your multiplayer character. Depending on how much the health the enemy has, your XP gained will vary accordingly. Completing online matches will reward you Credits to purchase in-game equipments for your multiplayer characters, such as weapons, mods, power bonuses, etc.
You can choose a different multiplayer character with different race and class. Each variation has different sets of Powers to be used. For example, an asari Vanguard has exclusive access to Lift Grenade, whereas the human Vanquard does not have it. However, human Vanguard has exclusive access to Nova but the asari Vanguard does not have it. Choose a proper Class and race to suit your own playstyle online. Be reminded that each multiplayer character in the game does not share levels, but individually.
Your multiplayer character level's is capped at 20. Once your multiplayer character reached level 20, you can import the character to the single-player mode as a War Asset, boosting your EMS.
The multiplayer mode is not essential to complete, but it is an incentive to play because completing online matches allow you to boost the Galactic Readiness in the singleplayer mode. Galactic Readiness acts as multipliers for EMS gained from the War Assets. Essentially, if your overall Galactic Readiness is high, your EMS points gained from the War Assets will increase as well. In short, you don't have to do a lot of side quests in order to get the minimum EMS requirement. It is noted that to to obtain a certain extra scene in one of the endings, you need to get more than 5000 EMS points. To obtain that extra scene, it would be best if you play the multiplayer component to boost your Galactic Readiness to get more EMS points.
The multiplayer is good, and provides great incentive to play. Unfortunately, there is only one type of match to play, which is to survive enemy waves.
v) Gameplay conclusion
This is the final Mass Effect game that concludes Commander Shepard's storyline. It is one of the best games I have ever played, albeit some flaws that prevented it from being a true masterpiece.
Storyline

Commander Shepard is on a mission to unite every species in the galaxy to defeat the Reapers once and for all.
This game takes place after the events Mass Effect 2: Arrival. Commander Shepard is suspended from military action, due to his/her actions of destroying the mass relay at a batarian space. While he/she is on Earth for meeting with the Alliance Council, the colossal machines that came from the dark space called Reapers have attacked Earth. Commander Shepard and his/her good friend Anderson work their way to escape from the Reaper's attacks. Although Shepard managed to escape from Earth, Anderson stayed on Earth and tasked Shepard to bring reinforcements from every species on the galaxy to defeat the menacing Reapers. On his way to convince other species to work with him, he must battle against the Reaper forces, as well as Cerberus forces.The storyline is nearly perfect. Great character interactions, good story pacing, interesting character developments, good plot twists, and well written. Unfortunately, the game's three main endings are not that good and not satisfying. The three main endings are abrupt, not well developed and not well explained. The endings did not explain properly what are the consequences after certain actions being done in this game as well as previous Mass Effect games. This is a truly disappointment to many Mass Effect fans, including me as well.

Old characters from previous Mass Effect games will return, as well as new ones in this game.
By importing your save file from Mass Effect 2 (in turn also importing Mass Effect save file), certain characters and story elements will be present in this game. Provided on what have you done in Mass Effect and Mass Effect 2, previous characters will return in this game in some form of appearances. Characters from Mass Effect like Wrex, Ashley, or Kaidan may or may not return depending on what you have chosen in that game, and this also applies to Mass Effect 2 characters such as Legion, Tali, etc if they are alive or dead in the final mission of Mass Effect 2. Other minor things such as the results of completing side missions from the previous games will return as well, and may help you in fighting the Reapers.
If you are new to Mass Effect series, there will be a default storyline where certain story elements are not influenced from the previous Mass Effect games. Although, this is a poor choice, and obviously you will like to play the series from the first game to know the storyline of the series, then proceed to the second game and the final game with the decisions you carry over from each game.
I am very satisfied with the storyline, complete with the decisions carried over from previous games. My main gripe with the story area is the weak, abrupt, and under-developed endings.
Gameplay
i) Importing section (Singleplayer)

Import your completed Mass Effect 2 save file to this game.
As in Mass Effect 2, you can import your save file from Mass Effect 2 to carry over your decisions in the Mass Effect and Mass Effect 2. Certain details such as gender, class, and personal history will not be changed in this game, but you have the option to carry over your imported face or create a new face for your own Shepard. Most major decisions made in Mass Effect and Mass Effect 2 will be carried over to this game, showing continuation between each games and may bring major impacts to the storyline itself.
For PS3 players, you do not have the luxury of playing the first Mass Effect game because it is a Microsoft exclusive game. The only way for you to carry over important decisions from the first Mass Effect game is to purchase and play Mass Effect: Genesis, an interactive comic that details significant events happened in the first game and allows you to choose important decisions to be carried over to Mass Effect 2 and Mass Effect 3. New copies of the PS3 version of Mass Effect 2 will have the free download code for Mass Effect: Genesis, but if you are playing the second hand copies of Mass Effect 2, you need to purchase it from PlayStation Store.
ii) Exploration, progression and customisation section (Singleplayer)

Travel to different planets to complete your missions.
Exploration is similar to previous Mass Effect games, where you need to move your character from a location to another and talk to someone to progress in a Mission. While in the Normandy and the Citadel, you can move around and talk to people to initiate interesting and insightful conversations, or initiate side quests by talking to them.
The Galaxy Map is the same as the previous games, but now you have Reapers invading in certain Systems in the galaxy. You can scan planets for War Assets, but by doing so, Reapers will be alarmed to your presence and will try to catch and destroy you if you use scan the planets too many times. If they have caught up to you, you will get a Game Over, and you need to restart your most recent save again.
After finding planets that have War Assets, you can scan the planet and send a pod to retrieve it by following the pointer on your radar. It can be either Credits (in-game money), or War Assets that help you in the final battle against the Reapers.

Complete side quests and optional missions to obtain more War Assets.
War Assets have their own Effective Military Strength (EMS). By completing missions and side missions, you will obtain War Assets that will boost your EMS to fight the Reapers. Provided that you do not have enough EMS when you are fighting the Reapers in the final battle, the consequences might be fatal. It is best if you complete side missions to achieve the minimum EMS to fight the Reapers.
Each Missions have their own objectives, and you can only progress in the Mission by completing the require objectives. Some missions have Priority in the name, whereas some don't. By only completing the Priority missions that you are allowed to progress in the game. Completing missions that do not have Priority are optional, but it is best to complete them to obtain more War Assets.
Side quests are obtained by hearing NPCs talking aloud in the Citadel. Most of it require you to scan a planet, and retrieve something from there. It is quite boring to do so, but most of the side quests offer you some good rewards such as War Assets and Credits. The method of retrieving something from a planet is the toned down version of Mass Effect 2's mineral scanning.
The Morality system returns in the game, but it also features the Reputation system. Reputation acts as a multiplier to your Paragon and Renegade points, and you will get more Reputation points by completing Missions and Side Quests. The conversation system is the same as in previous games, where the conversation come in a form of dialogue wheel. You can inquire further information from a character in the game, or ask him/her to do something. Certain important decisions can only be done by choosing a Paragon option or Renegade option. You can only choose the Paragon or Renegade options only if your Paragon and Renegade points are high enough. You can also interrupt a conversation by doing a Paragon action or Renegade action. Doing so allows you to change the intended outcome of the conversation and also nets you more Paragon or Renegade points.
When you play a default new game, you can customise on how your Commander Shepard looks like, gender, class, and personal history. Some of these details may affect certain things in the game, such as your potential romance interests, your power sets, etc. If you import the completed save file from Mass Effect 2, all of those details will be carried over to this game.
Your Shepard's appearance can be changed, such as you can change his/her casual clothes, or customise armour parts for combat. Some armour parts may have different bonuses, such as slight health bonus, etc. So try experiment a bit with the armour parts. In addition to that, your armour will look different if you use a new and different parts. You can also purchase complete armour sets from the Stores, but they are quite costly, and you better spending off your Credits in buying other stuffs.
iii) Combat section (Singleplayer)

More refined combat from Mass Effect 2, as well as certain combat elements taken from the first Mass Effect game.
The combat system is similar to Mass Effect 2 games, with certain refinements. This time, you can use heavy melee attacks that allows you to kill enemies close by easily. If you do not like to use it, you can use the normal melee attack for a quick kill. Pressing the melee button repeatedly will result into a combo melee attack.
Grenade returns in the game, albeit in a more traditional form of grenades that are often used in most third person shooter games and act as grenade Powers. Instead of a disc based grenades, the grenades in this game are thrown out like normal grenades in real life. Since grenades still require ammunition to be used, you won't be able to use it if you don't have any grenades. Grenade powers can be upgraded to improve it's potency and usefulness in combat.
Other than those two new additions, you have the ability to sprint infinitely, rolling to dodge attacks, and faster cover trekking. BioWare did a great job in improving both actions, since Shepard's movements are kind of limited in the previous game. Dodge rolling is an important feature in this game, since many enemies in this game are dangerous and relentless. The cover system is more faster and refined, as it allows you to quickly transition from one cover to another.
There are three main factions that act as your enemies in the game, which are Cerberus (human soldiers), Reapers (alien enemies), and geth (robotic enemies). Each faction have different style and enemies for you to combat with. For example, Cerberus often uses Atlas mechs to fight you, and Reapers often use Banshees or Brutes to fight you. Depending on where the missions or the side missions located, you will fight different factions of enemies.
Each enemy have their own Health points, which is brought down by shooting at them or using Powers at them. Certain enemies such as Banshee have extra HP called Barrier, which is extremely susceptible to biotic powers but is strong against normal gunfire. Depending on the toughness of an enemy, they may have extra health bar that needs to be depleted before depleting their real health bar.
Obviously, you will die if your health is depleted enough. Depending on what class you are, your character will have a Shield or Barrier acting as an extra health bar. Either one will regenerate over time if you stay in cover or being undamaged for a certain period of time. If your Shield or Barrier is depleted, your Health is in danger of being depleted by enemies. This time, your health have 5 bars, and if one bar is depleted, your current health will remain at 4 bars. Your health will be restored fully after certain conditions, such as using the First Aid power. First Aid power can only be used if you have any remaining Med Kits. If your squadmates KO'ed in battle, you can manually revive them by going to them or use the First Aid power to bring them back in action quickly.

Devastate your opponents with your powerful weaponry as well as Powers.
As in previous Mass Effect games, you have to use your high-tech weapons to kill off enemies. There are several categories of weapons, such as heavy pistol category and assault rifle category. Each weapons have their own pros and cons, so experiment on each weapon to suit your play style. Weapons can be bought in the Stores, or can be found while playing Missions in the game.
Unlike in previous Mass Effect games, this time, you can use all 5 types of weapons. However, each weapon have it's own Weight. Powerful weapons such as sniper rifles are heavy, whereas weaker weapons such as submachine guns are lighter. If your total weapons weight exceed your current weight percentage, your Powers will have much more slower cooldown period. Obviously, if your weapons are light enough, you can use your Powers more often. Choose weapons for different missions wisely.
Weapons in this game can be upgraded by purchasing upgrades from the Normandy store using Credits. The maximum level for a weapon you can achieve at first playthrough is level 5, and can be upgraded to level 10 (the maximum) in the next playthrough if you find the weapons again during missions.
The weapons mod system also returns in this game from the first Mass Effect game, albeit in more simpler and user friendly approach. Instead of extensive customisation on weapons, this game features more simpler way to mod your weapons, where each weapons can only have 2 mods at a time. Each mods have different effects, and should be experimented regularly. The mods can be found while playing a mission or by buying from stores.
Your Shepard have his/her own set of Powers depending on what you have chosen as your Class, as well as your squadmates. For example, if your Class is Adept, your Powers set will focus on biotic powers. As you reached a new Level, you will receive upgrading Points to upgrade a Power. Each Class have their own sets of active Powers and passive Powers. As you increase a Power level, you will reach a branching point where you have to choose one of the two Power bonuses. However, this do not occur at your Power's final level, but at midpoint of your Power's level, You have to choose three times between the Power bonuses before upgrading your Power to the maximum.
Of course, your squadmates have their own set of Powers, and depending on what their skills are, they might or might not be a powerful asset in battle. For example, Liara has powerful biotic skills, but her health is too low and she only has Barrier to make her last longer. Since each squadmates have unique Powers and weaponry, having a balanced team to offset your own Shepard's weaknesses is highly recommended. In most situations, having a team of soldier squadmate, biotic squadmate, and a tech squadmate is the preferable team matchup.
The level up system is similar to the first game. You will receive experience points (XP) by completing your sub-objectives in a mission, completing side quests, etc. As soon as you have obtained a new Level, spend some time on upgrading yours and squadmates' abilities. The maximum level in the game is 60, so you will spend quite some time if you want to get the maximum level.
iv) Multiplayer section (Multiplayer)

Play online with other players in Galaxy at War (Multiplayer Mode)
This is the first Mass Effect game that features a multiplayer component, called Galaxy at War. The multiplayer matches consist of entirely fighting waves of enemies in a map area. There can be up to 4 players playing in the match. For an online match, you can customise the difficulty, map, and etc to your liking. You can also choose a random match and play, but it is not recommended since you might be thrust into a very difficult online match.The multiplayer does not feature competitive play with other players, but cooperative play with other players, meaning no friendly fire. In the online matches, you need to fights waves of enemies (Cerberus, Reapers, geth) in a map. There are 10 waves, but some waves require you to complete certain objectives, such as disabling a device, hacking a device. After surviving all 10 waves, you will need to go to an evacuation area, and you will need to wait until a time limit runs out to complete the match.
Killing an enemy rewards you XP points to level up your multiplayer character. Depending on how much the health the enemy has, your XP gained will vary accordingly. Completing online matches will reward you Credits to purchase in-game equipments for your multiplayer characters, such as weapons, mods, power bonuses, etc.
You can choose a different multiplayer character with different race and class. Each variation has different sets of Powers to be used. For example, an asari Vanguard has exclusive access to Lift Grenade, whereas the human Vanquard does not have it. However, human Vanguard has exclusive access to Nova but the asari Vanguard does not have it. Choose a proper Class and race to suit your own playstyle online. Be reminded that each multiplayer character in the game does not share levels, but individually.
Your multiplayer character level's is capped at 20. Once your multiplayer character reached level 20, you can import the character to the single-player mode as a War Asset, boosting your EMS.
The multiplayer mode is not essential to complete, but it is an incentive to play because completing online matches allow you to boost the Galactic Readiness in the singleplayer mode. Galactic Readiness acts as multipliers for EMS gained from the War Assets. Essentially, if your overall Galactic Readiness is high, your EMS points gained from the War Assets will increase as well. In short, you don't have to do a lot of side quests in order to get the minimum EMS requirement. It is noted that to to obtain a certain extra scene in one of the endings, you need to get more than 5000 EMS points. To obtain that extra scene, it would be best if you play the multiplayer component to boost your Galactic Readiness to get more EMS points.
The multiplayer is good, and provides great incentive to play. Unfortunately, there is only one type of match to play, which is to survive enemy waves.
v) Gameplay conclusion

Overall gameplay has improved further from previous two Mass Effect games.
The gameplay of this game is simply magnificent, and it has improved further since the first two Mass Effect games. I am glad and surprised on how well BioWare did with the gameplay area. The only disappointment I had with the gameplay area is the lack of bosses, and boring side quests. Surprisingly, in the artbook included in Collector's Edition of the game, there is a boss design of The Illusive Man, but it was scrapped earlier on. I felt that it was a waste to scrap that design, since it would have been an epic final boss fight in the game. Side quests are not varied enough, and most of it requires you to find something from a planet by scanning it.