What makes a pop culture icon?

Would it be the effect of their contribution to a cultural movement? Is it the way they impact the time and the generation they are targeting? Or just how their exposure constitutes a defining characteristic of a given society or era?

As a child of the 80's I was heavily influenced by everything from saturday morning cartoons on TV to the music coming from the radio. Ian Curtis or Johnny Rotten are as iconic to me as Superman or Batman. Real people or imaginary characters, the incorruptible ideals of perfect superheroes or the human flaws and desires sometimes so desperately depicted in song lyrics - all of those influences affect us to the point of defining our character and personality, career paths and life choices.