Superman is the ultimate superhero. Not only does he beat Captain America but he beats all superheroes everywhere.
Nothing I can say will sum it up better than this Wonder Woman quote:
WW: Kal-El, the only thing that matters is that S. When someone sees that symbol they know they're going to be okay, because you are there. No hero, new or old, could ever be what you are, to us, to them, to the whole world. There will never be another Superman.