For a long time, I have been of the following mindset:
The greatest superhero and quite possibly the greatest character of literary history is the amazing, spectacular, friendly neighborhood Spider-Man.
Every superhero has underlying themes, a secret-secret identity. Superman has been an allegory for the immigrant (first-gen Eastern European Jews especially) and also a messiah figure, leading to various thought experiments as to the nature of God/infinite power. Thor does this, too. Batman is about coping with mental illness and the creation of surrogate family. Daredevil focuses on the Catholic themes of guilt and redemption through sacrifice. Fantastic Four is a narrative about a man using science to unlock the mystery of existence and the frontiers of reality while his family anchors him to humanity. Professor X is MLK. Silver Surfer is Siddhartha. Hulk is Frankenstein/Godzilla/Jekyll&Hyde. Green Lantern Corps? Hill Street Blues.
Spider-man has them all beat.
Spider-Man is all of that and more.
Spider-Man is a regular guy.
He never asked for his abilities. He didn't sign up for a military experiment. Didn't build a super suit or train for years in secret. Didn't even screw up a space flight or a bomb test. He just went to a damn science expo and shit happened.
And then he had to deal. Attempting to be selfish blew up in his face. Instead, he gets up each and everyday and (often to the detriment of his own wants) does what has to be done. His power is defined by his responsibilities and vice versa.
His potentional. His conscience. His conflict. His courage.
His is the story of us, one and all.