Robert Downey Jr. is switching sides in the comic-book battle of good vs. evil. The “Iron Man” actor will portray super villian “Doctor Doom” in the next two “Avengers” movies, Marvel Studios president Kevin Feige revealed Saturday at the San Diego Comic-Con event, according to People. Downey, 59, emerged wearing Doctor Doom’s trademark green hood and metal mask, surrounded by a crew of similarly attired actors. “New mask, same task,” he said after dramatically removing the face shield. “What did I tell ya? I like playing complicated characters.” Downey, who in March won an Oscar for best supp…