Disclaimer: I'm not an owner, I'm just a random shipper.
Evil Reasons
Every kid wants to grow up to be a superhero. I mean, sure, if you ask them, they might say firefighter, or policeman, or doctor, or whatever, but that's only because they don't think superhero is an option. If they were born with powers, OF COURSE superhero would be their first choice.
So why is it different for me? Why do I want to be a supervillain instead? I've got a lot of reasons for that. A lot of reasons.
Firstly and most obviously, supervillains get way cooler costumes and names. What sounds better, Captain Do-Gooder or Doctor Destructo? Yeah, that's what I thought. And just look at those lame superhero costumes. All that brightly colored spandex. Yuck. The only superhero with a halfway decent outfit I've seen is Batman, and even he has those stupid looking horns on his head. Now, villain costumes can be lame, too...but it's not a requirement. And the options are just better in black.
Secondly, villains have a lot more freedom than heroes. Heroes have to obey authority and uphold the establishment and all that schtik. Well, I've got news for you. Sometimes the establishment sucks. And obeying authority ALWAYS sucks. If I lived in a family of supervillains, I wouldn't get in trouble for breaking the rules at school, I'd get praised. As I should be. Breaking stupid rules is just common sense, right? And forget about homework. See now? Villainy starting to sound pretty good, huh?
And right along with that goes EXPECTATIONS. Just like Green Goblin said, what people love more than a hero is to see a hero fail. They hold you to these impossible standards, and then rip you to shreds when you fall short, even if you did ten times better than anyone else would have in your place. It's completely bogus. The constant scrutiny, like your life belongs to the public instead of yourself. Villains never have to deal with any of that. I do what I want, and I won't have anyone judging me.
To be perfectly honest, though, it's much more simple than that. All of those reasons are true, for sure they are, but I'd still be a villain even if they weren't. Not because I enjoy evil (I do), or because I think evil is cooler (it is). Rather than saying I've chosen evil, it's more like I've recognized that deep down, no matter what I choose, evil is just what I am.
After all, a good person, a decent person, a SUPERHERO, doesn't want to bang his sister's brains out.