He saved the human race when he kept himself from releasing the virus
Good point. That's two for Peter.
Peter was an incredibly good person. Hiro was an impossibly good person. Sylar was a very very evil person. This has been clear from the beginning. I mean, they even said in one of the episodes this season about Peter: "Nobody is that good..."
And then true we had these characters like HRG, Nikki, Nathan and lots of others that we're neither good nor evil.
And while I understand the fact that Peter, Hiro and Sylar (and Mohinder for that matter) could've been one dimensional because of the extremes they represented, I for one liked them for what they were. But now it seems that turning evil is just as simple as flciking a switch in somebody's brain. You cannot tell me that makes for healthy character development. To me it is lazy, contrived and all in all subpar characterization. And frankly I'm kind of worried everybody seems to like this episode so much.
The turn to the darkside is a journey, not a lightswitch.
You're right, and I also disagree. Peter was a good person, it takes a lot to be an empathic hospice nurse. Hiro was an idealist, but he was, as far as I could tell, primarily self-centered. Until he 'grows up,' to me, he's still playing hero. Sylar was very twisted, and a bad person, but he still had a conscience that was able to be pricked by innocent death that fell outside of his 'interests.' I too, loved these characters for what they were, but I never let myself think that these were 'good guys' and 'bad guys' because, to me they were too well-realized to be categorized into comic book cliches.
Of course it shouldn't be a lightswitch, like they've done this season, but we already saw in S1 that a little dose of reality (Ando's death) turns "impossbily good" hero into an Anti-hero badass who's sole motivation is the primarily selfish one of getting his best friend back. That's right, according to S1 Future Peter (an experienced Empath, btw), Hiro twisted time to get his friend back. It wasn't until his Five Years gone that Future Hiro actually got up the real selfless guts to sacrifice himself, and then again, it was for a past version of himself.
Imho, Hiro is easy. Having one of his heroic idols (Takezo would have been perfect) break his heart could have ripped Hiro from his idealism, and sent him at the very least, into the 'normal people' range that all of the other characters inhabit. Malicious or not, he could have been naturally turned to a negative influence.
Peter is easier in many ways. As someone who is used to death, he is perfect for being the 'greater good' type of villain and honestly, all it takes is one power trip. As soon as he thinks he has the power to fix things that shouldn't be fixed he'll try. That was actually the only good thing about Future Peter... he logically SHOULD be a villain, jacking everyone's lives up for the greater good... the only thing they messed up with him is trying to make him heroic... there's no reason Future Peter should ever be too late for anything, or have trouble finding anyone instantly. He should have no challenge popping the nor should he be 'running' for his life.
Sylar, of course, is too twisted to naturally develop into a heroic figure. Of course, they had a great storyline with Haitian amnesia that would have certainly turned Sylar into a hero, at least temporarily.
But even with or without all this, Peter "no one is that good" Petrelli was the explosion from S1 and Nathan "Billain" Petrelli was the one who saved the day. Peter was the villain's dragon in S2, and the virus wouldn't have gotten out without him. Morally grey, and switching from heroic to villainous and vice versa was a basic theme of the show. Just because they're doing a bad job of it doesn't mean it should be included.