Superman was born on the planet Krypton, but while he was still a baby he was sent to Earth in a spaceship before the planet Krypton was destroyed.  Once he landed on Earth, he was found, and adopted by Jonathan and Martha Kent.  He was named Clark, after Martha's maiden name.  Clark was raised up in Smallville, Kansas.  As Clark grew older he found that he had incredible super powers.  Clark's mother and father encouraged him all throughout his teenage years to use his powers for good instead of evil.  Jonathan Kent made sure that Clark knew how important it was for him to keep his superpowers a secret from others and to keep his secret identity as Clark Kent.

The secret identity: Clark Kent

Clark Kent is a very important element of Superman's lasting effect as a superhero.  Clark Kent is a very meek, and meager guy.  The personality of Clark Kent is the opposite of Superman's.  Where Superman is strong, and courageous, Clark Kent is a coward, and a weakling.  Superman will stand up to any foe fearlessly, while Clark Kent will back down, and be submissive to everyone, especially Lois Lane.  This is the truly weak part of Superman that everyone can identify with.  Every last one of us has at least one of the character traits that Clark Kent has, and so we can see ourselves in his position dealing with people, and yet always being walked on. 

Superman's Vulnerabilities

Superman's vulnerabilities allow readers and viewers to identify with him.  As long as Superman has a weakness he is merely a superhero rather than a god.  People lose touch with the hero as soon as he loses all weaknesses.  The story becomes a waste of time, and becomes boring, because a god has power stronger than anything mortal, and therefore the outcome of the story is already known, and the god is victorious.

Superman's main weakness is Green Kryptonite.  Green Kryptonite cripples Superman and takes away his ability to function.  Countless foes have tried to use the substance against him, but are constantly foiled because of Superman's lead suit that can stop the rays of the Green Kryptonite.  Green Kryptonite are radioactive pieces of the planet Krypton that are left over after they planet was destroyed.  Green Kryptonite is indestructible just as everything else that came from the planet Krypton is.

Another weakness is Red Kryptonite.  Red Kryptonite is a rare form of Kryptonite that passed through a cosmic cloud, and became altered by it.  Superman is affected by Red Kryptonite in weird ways.  It can cause Superman to lose his powers temporarily, or it can cause him to transform into a monster, or even make him immune to Green Kryptonite but vulnerable to gold, silver, and aluminum.  Red Kryptonite can only affect Superman once however, and it is not invulnerable as Green Kryptonite is, and can be destroyed.

Superman can also be affected by Magic as well.  Not all Magic can affect him however.  Magic does not hurt Superman, it can only detain him, or hold him in place, incapable of fighting back.

Superman Stands In His Own Time

Superman has a lasting effect in this world because he never ages.  He has been around for so long, and yet he is still a man that looks to be in his thirties, and never ages a day.  At the beginning of every episode everything is set back to the way things were originally, as though these were only possible stories that could have happened to Superman in his lifetime. 

Umberto Eco: The Role of the Reader

Umberto Eco discusses the temporality of Superman, and that he never ages.  Superman is within a time of his own, but he is not really a part of time at all.  In The Role of the Reader, the discussion about Superman's temporality is in that there is no link between any of the episodes in order to keep him from aging, because any signs that he would be growing older would bring about the eventual death of Superman.  The only time that is evident in any story about Superman is the time in which the story is told.  Superman becomes a timeless icon, because he never ages, but always stays recent with the times, and everything that happens in the story happens as the reader is reading it.