Listen guys: i accept DMC 3 and 4, and even DMC 2 Dante as Dante.
Because they didnt change him that much. DMC 2 dante was very weird personality wise though. He didnt seem "Dante" at all.
Yes, but it's nearly the same thing about your topic in the DmC forum about Eva's wings, this could be perfectly explained as Dante is a half-breed who probably ages much slower to other human beings (like Lady or Patty), the same thing that happened to Dante happens to Vampires and Elfs on RPG (D&D, Vampire: The Masquerade) fantasy worlds regarding humans: they couldn't sustain a longtime emotion about humans as their notion of time is very different, even if they have the same feelings inside they became much more "cold" because if they care too much about some humans sooner or later they will die and they will be left alone in the world until them die too. That's why i think Trish is an interesting character to hang with Dante, she's a demon too and can stay with him unless someone kills her.
Some ideas about Nero and Vergil just popped out from my head right now:
As i said, they have total control to make changes on the storyline and this is much more true about how older the characters is (obviously this have to match on how they looks like), as they are never told in the games. They could make a timeline that fits that Vergil is Nero's father thing, and i've actualy come with an interesting relation to make the already existent lust for power in Vergil more true, visualise this scenario:
A kind human family compound by a little girl just a bit more older than Vergil, and a young couple that are her parents who have, let's say, a rare disease refuges Vergil when found him "lost" and slowly regaining his memory of the recent events (he remembers he had a brother, but as time passes and he don't find him, he assumes that or he's dead or that he's safe anywhere), it happens a little time after his mother death (they could take inspiration here from the manga that shows a child Vergil being tortured by some demons, discovering a good portion of his demonic power, including his devil form) and as time passes and they grew up, Vergil was becoming more and more attached to that girl and is seeing her parents (and his second family) dying slowly and again realizing that he is powerless when it comes to matters of life an death, mainly when it comes to human life. As time passes, her parents die, the two kids start to live for themselves as "normal humans" (demons still found Vergil because of his demonic power, so they kinda not live an average human life, that can explain why he is an skillfuly warrior too) and he impregnates her; but them they discover that she has the same disease as their parents and is dying too, this could be the kickstart to Vergil interest in the Black Arts and his father's power, he went to study the Black Arts and became obssessed with the idea to give his lover demonic power too, he knows that he's nearly unaffected by illness and that demonic power could save her. Then he discovers a ritual similar to that Arkhan used to get his demonic powers, he has to sacrifice a pure woman in order to give her lover the demonic power and he sees this as the only way to save her, simplifying things: he fails on that subject because of his human emotions (that were kinda cultivated by the time he spended with this human family that treated him like he was blood-related to them) and this would give a great background to explain why he's trying to get rid of his human side and becoming more of a demon, his mind is twisted because of his human emotions, he desires to be a cold-hearted demon and a guardian who seeks the power to protect anyone he loves, all this at the same time. He's lost in his own sadness and tough experiences (and forces himself to not show this) but without depressing himself and trying to correcting all that he (thinks) done wrong in the past. Nero is born and again Vergil has a loved one dying on his arms, he's lost one more time and his humans feelings are leaving deep scars into his soul and now it is becoming darker and darker, taking what is left from his scattered humanity he take a decision to make his newborn son not live the same disgraceful life as him, the better way he finds to protect his own son from having the same destiny as himself, is to let he grew up as a human amongst humans and far from his father and his heritage then he goes into another quest: Along his studies Vergil gets to know about Fortuna and their "story" and obssession with Sparda, he makes contact with the elders of Fortuna, defeats a load of their army man to prove that he's indeed a Son of Sparda and teach them about the Black Arts, he says that he probably will be back to ask a favor in payment to this knowledge he gifted to them. And here is when Nero comes to scene, he was send to an orphanage by the time while they don't know what to do with him, ironic his destiny among the humans became very similar to that of his father who is to be embraced by a human family. So, the events pre-DMC3 and DMC3 starts, when he meets Dante again and beat him to show that if he is not powerful enough he will be condemned to a miserable fate (like he was, but don't explain), this atittude can be seen as a distorted proof of the love Vergil feels for Dante, he want Dante to grow stronger because he thinks that it's the only way they were meant for living (this could be relate with the books he read about the Black Arts, who is basicaly knowledge that humans acquired about demons and their powers, and to a certain extent praised the demons and we know that the unwritten law of demons is power by itself).
The rest is story. And to make something like this is just a matter of reviewing the timeline and explaining things better (as i already discussed on the first topic). I think that old DMC series has much potential to be a deep and touching story if it would be expanded and explored, because it already has interesting and cool characters. Vergil himself is a very intruiguing one, you can see he's fighting his human emotions but we have no idea why he have that strong desire to be powerful and more a demon than a human.
See, i'm not even a good writter and could think in something like this, and i did this in like... 30 minutes. This is why i don't think the series needed a reboot, it's not messed that hard.