The whole "Superman is too strong argument" is such an uninformed statement and pretty much confirms that someone knows nothing about the character.
Anyway, in my opinion it's Spider-Man. Well, the Spider-Man of the past 30 or so years. That character has literally done everything he possible can and he's now an adult who behaves like a freshman in high school. He's annoying, whiney and has never grown up. I've been saying for years that Marvel needs to kill off Peter Parker and let a new actually interesting character take up the mantel.
... Miles Morales says hi
There's a five part comic series about the death of Peter Parker (Well, it's called Death of Spider-Man, but yeah), although it only takes place in the Ultimate universe, you might want to check it out... basically, Peter Parker is dead, and Miles Morales is the new Spider-Man now, he has a few different powers, and his costume looks pretty cool.
Why read the comic when you can watch it! It doesn't show any Miles Morales stuff, though. Still, it's a good video.
