People are comparing it to a film ruining The Joker, but can't seem to understand that superheroes like Batman and Superman have been in the forefront of mass media for decades and people have basically been indoctrinated to know their peanut gallery of villains. Just about everyone knows who The Joker is, or The Riddler, or Penguin, and Catwoman.
Prior to 2008, most people had no clue who any of Ironman's villains were, or really even who Ironman was. He was really a B-Tier comic hero until that first film and RDJ's eccentric performance thrust him into the spotlight. The masses are really new to this character, he's new to the spotlight. Characters like Batman and Superman have lived in the spotlight for getting over a half century. As such, his villains are more blank slates.