Because we can relate to the superheroes and even the villains. The characters always have something different about themselves that makes them unique, intelligent, and advanced enough to do something far greater than an ordinary person. I like X-Men because I can relate to the mutants feeling different from society, and plus the action and the art is great.
_________________
"Imperfection is beauty, madness is genius, and it's better to be absolutely ridiculous than absolutely boring" -Marilyn Monroe