Robert Downey Jr. is eminently capable of dying from drugs, but it seems kind of harsh to ask that of him.
Yet, "Iron Man" wouldn't have been nearly as big of a hit with anybody else in the lead. I'd guess that Downey added $100 million to the domestic box office. It's kind of like a sportswriter saying, "We shouldn't give the MVP award to Peyton Manning because he makes so much money already, so I'm voting for the criminally underappreciated long-snapper on the Detroit Lions. Look how much they had to punt this year!"