Since my favorite hero is Spider-Man I can imagine him living as Peter Parker and making new friends,and enemies in ponyville :)
My favorite superhero is Frank Castle (The Punisher) so...I don't think that it will go to well giving the methods that Frank have to "deal" with criminals...
My Hero Is Ben 10 so i can see his Omnitrix gaining Pony DNA and the ability to turn into a pony and back to human as he pleases :3
(i know ponies are not aliens!)
and instead of crystal ponies lets have some diamond ponies (diamondhead)
and Jet Ray Pegasus Pony?!
then theres the Xlr8 Earth Pony!
and Clockwork Unicorn Pony?