I was always a fan of Spider-Man and most superheroes. There aren't a whole lot of little boys out there that aren't.
In a film you only get two hours to do this big arc and so you have to pick and choose your moments carefully, but with television you get to take your time and just take it episode by episode and discover new things.
My mentor Jon Simmons introduced me to the Stanislavski system, which is so heavy on back-story. So you write and write and write these back stories about a character and then you throw it away. So then on set, if it doesn't come, then you didn't do your work.
It's just so much more fun to play bad than good. Plus it's just good to get that out of your system so it doesn't show up in your personal life.