People like idealized figures, although they like avatars in general, embodiments of a particular 'thing'. Even though Al-Qaeda was highly decentralized, we still liked to portray it as Osama bin Laden. Thousands of people worked toward abolition, but we always envision it as Lincoln. The American Republic was founded on the efforts of a third of the American population, but we usually boil its heroes down to Washington, Jefferson and a handful of others.
It's nothing new. Human society has done this for its entire existence. We tend to find concepts, embody them in unique imagery, and the like. Superman has always been that for me. I mean, I'm religious, and so Jesus Christ is obviously the king of my mental pantheon. I don't have any problem saying Superman, with his big bold blue suit and red cape, just as willing to save a cat from a tree as to push away a planet, is a huge influence in my life though.
We're talking about a man with the power of a god, who could dominate society if he chose to, a foreigner, an immigrant, who instead chooses to live among mankind, who ideally fights so that they become inspired to take up the fight themselves, who gives up his life and freedom to help those around him. A perfect world wouldn't need a Superman. I think one day he'll be happy if he can just be Clark Kent. Until then, when I'm bogged down by the shades of gray that is reality, it's nice to be able to grab hold of the simple concept of trying to do right to each other.