Been preparing my answer to this one
Pokemon Silver - Took up 300 hours of my life and I adored it!
Legend of Zelda - Majoras Mask - Moreso than OoT, this game enthralled me and I still replay it from time to time
Legend of Zelda - The Wind Waker - I'm charmed by its looks, humour and overall fantastic gameplay! The sailing gets boring but otherwise it is such a fantastic title.
Assassins Creed 1 & 2 - Both games were brilliant, the second more so than the first. Adored them, although I hope ACIII fixes my niggling problems with the games
Bioshock 1 & 2 - Such a beautiful game, and such a great story. The second is a well deserved revisit, whilst the first is a gaming legend. Would you kindly buy it and play it ^_o
Batman Arkham Asylum - What can I say? Its an awesome game about Batman.
InFamous - Just platinumed, and it was amazing! I'm a huge fan of Comic-Book games, and this is superb!
Devil May Cry 3 & 4- I love both of these titles, and spend lord knows how many hours enjoying them - bring on DMC5! ^_^