A topic that has intrigued every fan of superman is which is the "real" or "leading" persona of hislife, is it Superman the super-hero symbol of Truth, Justice and the American Way,is it clark kentthe kid from smallville whowas raised by the Kent family or Kal-El the last son of Krypton sent to earth after thedestruction of his planet.One thingis certain Superman is a mix of the three identities.The destruction of krypton , the Kents and thepowers to help the human race are part of a triangle that led superman to become the man who istoday.
Superman Through The Ages!
In the beginning of the Golden Age Superman had yet to get a distinct origin (Superman got his characteristic origin for the Superboy title).Superman was the last son of Krypton who was found and raised in an orphanage, having his powers already from a very young age Superman had a lonely childhood.Hitting adulthood he left to use his mangificent powers for good.Supes got a job at the Daily Planet, the center of the news world to be kept informed.To blend with the staff he adopted another identity.Clark kent was the new reporter of the daily planet,strong,courageous and a moral rock, Golden's Age Clark Kent is quite different from the Modern Age version. As the years passed Superman origins was explored and drastically changed.He was now raised by the kent family,he adopted the mantle of the superhero at a younger age(superboy!) but had still maintained the same personality and beliefs. To conclude, in the pre-crisis continuity the leading identity of Superman is well......Superman.Clark being just a disguise.
After the Crisis of infinite earths Superman's character changed completely.Clark now is alive he has a past,relationships and definite place in the mythos of superman. Clark got his powers slowly reaching adulthood and he became a humble,righteous,farmboy from Kansas.Superman is no more a god among mortals, now he is one of them.Having the support of Ma and Pa Kent, Clark is now much less alienated.Using his powers for good Superman is now the disguise Clark Kent use to fight crime.Also Kal-El takes place as a leading part of The Superman.
If you want a more detailed approach about the differencies of the Pre-crisis and Post-crisis you can look at the blog of http://www.comicvine.com/forums/gen-discussion/1/man-or-superman-part-1-what-byrne-did/576303/"Man or Superman Part 1- What Byrne Did"
Superman Depends On The Writer
Superman's change since Byrne's origin
Because of the various media and different portrayals the dynamics between the THREE IDENTITIES changed all the time. Making the readers to ask "who is Superman".The right answer changed with every storyline,series,comic etc. Example : Superman TAS portrays a more down to earth superman while Superman : For Tommorow shows the importance of his kryptonian inheritance.
New 52 Superman
Another great change for the man of steel brought the new 52 relaunch.
Grant morrison created a more Golden age superman for the relaunch,bringing the character to his roots,Superman takes the spotlight,leaving Clark and Kal as secondary roles of the man of steel.Though the Superman title doesn't follow the same tactic.The reader is free (or forced) once again to choose his Superman.Let's hope DC will sort it out.
Superman Changes With The Audience
Superman's portrayal changes with the reader.It is no coincidence that superman fell down to earth during the dark age of comics.The readers didn't believe in the idea that a Demi-god who owns nothing to humality is doing all those feats for them.Now Superman changes again with the readers to a mighter,higher version of himself who's main mission is to help everyone he can human or alien.