Ryan_Crown
Troubadour
Which is basically the same thing fiction writers have been saying forever: almost no one sees themselves as the bad guy. Probably not even serial killers see themselves as bad guys. Hitler certainly didn't. But that doesn't mean they aren't the bad guy.
I've found that for me the most compelling (and often scariest) villains are the ones who absolutely believe in the rightness of their cause, the fanatics willing to commit the most evil acts because in their minds it truly is for "the greater good". Not that there's anything wrong with villains like the Joker who completely embrace being the villain, but I think those villains are much harder to get right.
As far as "grey" stories compared to good vs. evil, I have to agree with Gryphos -- it's way too easy when you're trying to make all your characters grey to have them all end up various degrees of bad. Because if everyone's strictly in it for themselves and no side has any moral high ground, that's really what it feels like.
Personally, I want my stories to have a hero, not just a protagonist. Even if he's a flawed anti-hero, I want to feel like I can root for the main character to succeed because he does have the moral high ground in whatever conflict the story puts him in. Even if that makes the story "less realistic" I've very okay with that. If I want reality I'll watch the news.