Without a doubt I would say Chris Nolan's Batman.
I've always liked Batman and was also a fan of Green Hornet with Bruce Lee as Kato. I think what I liked about them was they were "human beings" and not "aliens" from another planet. Their powers came from their intelligence and innovatice gadget inventions. They had character flaws as well as internal demons to cope with.
As far fetched as it is, it seemed more plausible to me that a billionaire might have a dual identity fighting crime than having some alien fall to earth to fight our battles. lol
Spiderman and Hulk were also among my tops. However in both of their cases they were aided physically/internally by outside forces (radioactive spider and a lab experiment gone bad)