An essential characteristic of the superhero mythology is, there's the superhero, and there's the alter ego. Batman is actually Bruce Wayne, Spider-Man is actually Peter Parker. When he wakes up in the morning, he's Peter Parker. He has to put on a costume to become Spider-Man.
And it is in that characteristic that Superman stands alone.
Superman did not become Superman, Superman was born Superman. When Superman wakes up in the morning, he's Superman. His alter ego is Clark Kent. His outfit with the big red "S", that's the blanket he was wrapped in as a baby when the Kents found him. Those are his clothes.
What Kent wears, the glasses, the business suit, that's the costume. That's the costume Superman wears to blend in with us. Clark Kent is how Superman views us. And what are the characteristics of Clark Kent? He's weak, he's unsure of himself... he's a coward.
Clark Kent is Superman's critique on the whole human race. Sort of like Beatrix Kiddo and Mrs. Tommy Plympton.
Bill, Kill Bill