With other comic characters, I usually simply refer to the costumed name, but so much of what makes Iron Man compelling is the man behind and under the armor. Tony Stark is a study in dichotomy, a man both shallow and deep, brilliant and surprisingly obtuse. Stan Lee's 1960's Marvel Comics were rarely subtle, and Stark was no different. A heartless playboy who invented weapons, they attacked his heart and made him a weapon, and the result was a belated maturation for Stark, and the realization that he had a greater obligation than his own wealth and pleasure.
The Stark of the comics is an often tragic figure, a man not born to heroism. It does not come easily or readily to him, and the distinctions drawn between him and Captain America are apparent, culminating in the Civil War saga. Stark's struggles to reconcile to the identity and responsibilities of Iron Man drive him deeper into alcohol abuse, and the Demon in a Bottle storyline was cutting-edge stuff for an industry often neutered by the Comics Code into Saturday morning cartoon quality fare. Like so many real people, Stark's greatest foes were usually in the tin suit with him.
I was skeptical about the casting of Robert Downey, Jr. as Iron Man. I could see the playboy angle, but I wasn't sure how the fast-talking irreverence would play, since comic Stark was usually pretty straight-laced. Well, it worked. It worked so well that I would argue it is one of the more perfect superhero casting choices ever, along with perhaps Christopher Reeve's Superman. Downey inhabits Stark's persona completely, capturing the isolation and despair, but also infusing a character who could become stodgy in the books with a kinetic energy and restless charisma that makes the three Iron Man movies (and the Avengers installments) among the best of the genre.