He's a Kryptonian, a superior form of the human race. Not perfect, but superior. Also, the Smallville series has shown that he, like any other adolescent growing up, faces the same troubles that humans do (though in this case, it's not puberty or career choices, but his developing powers). Nonetheless, he learned to overcome them.
Ah, well if we are working with non-standard realities, then the Ultimate Iron Man out does Supes again, since that one grew up with the morals that regular Iron Man "woke up" to one morning. Though, he is also more “super” than regular Tony.
But you bring up an interesting point. Superman
is inherently racist. Or more seriously, superman is something that no human could aspire to. But Iron Man, he is something that you could aspire to be, and succeed.
This raises two interesting questions:
1. Do you need super-human abilities to be a super hero?
2. Can you buy super-human abilities?
Considering that Iron Man counted under the Superhero Registration Act, or whatever that thingy was called, #1 would seem to be yes, in which case yes, you can buy super-human abilities (such as Iron Man's armor).
Bats is an interesting case because while Wayne's "power" is that he is rich (whereas Tony's is that he is a genius, which made him rich), batman lacks all fantastical elements (except for the old live action TV series). Is Batman a Superhero? If so, then perhaps what makes a superhero a superhero isn't their powers but their bravery. Supes is brave at times, but not on a daily basis. When the only things that can hurt you are your home and magic, there isn't must of a personal risk in saving people. Iron Man, thus, would be more of a superhero since he is just a fragile, breakable human being. Bats, however, more so.
And Batman does have the best rogues gallery out of all three. Sure, Lex is cool (particularly the Smallville version), but beyond that... meh.
He has also demonstrated an ability to regularly exercise mercy when confronted with his enemies, a trait that Tony Stark doesn't share.
Again, because Tony is human. Also, Doomsday. What was Superman’s reason for fighting him again (or indeed, Doomsday's reason for fighting Superman)?