Superman, originally from Krypton, was found as a baby in Kansas. That makes him as American as KFC I guess. Batman is from Gotham which the Americans want as their own much like they want Iraq and Basmati rice.
Superman is a fashion disaster. As Superman he wears a blue bodysuit with red underwear and an S emblazoned on his chest like we would not recognise him otherwise. In his day job as Clark Kent, he dresses even worse, boring outsized spectacles and pensioner suits.
Batman is dapper, both in his Dark Knight working clothes and his Bruce Wayne suits. He is also the only super hero to coordinate the colour of his underwear with the rest of his outfit. Superman's alter ego Kent is a timid reporter with a steady girl Lois Lane and a boring life. Wayne is rich, single and fun.
But where Superman scores bigtime is transport. The man can fly. He just needs to stretch one hand forward and it's a standing take-off. Batty boy has a black Lambhorgini he calls Batmobile and it has cool stuff like an intimidate button, but he can't fly. Well, he can with cables and hooks but not London-New York like Superman.
Batman has no super powers. His powers have been acquired by hard work and money, mostly money. He is a bit like James Bond but doesn't drink vodka. Come to think of it neither does Bond now. Superman is all super power since he has no money to buy power and they don't accept Krypton cards anywhere. So, when they say superman "is faster than speeding bullet" it's natural ability dude. Take his blood test if you don't believe me, he is clean.
And finally, Superman's adversaries are largely boring. Batman battles a galaxy of big ticket villains including Jack Nicholson, Heath Ledger and Jim Carey. But then he hangs out with super gay Robin. Why.