Han Myung-Gu/WireImage & Paramount Pictures/Photofest 1 of 10 A superhero franchise is only as good as the actor playing the lead role. And when they do a terrific job as the superhero they are portraying, such as Robert Downey, Jr. in "Iron Man," it’s hard to imagine anyone else filling those shoes. However, the role that thrust Downey back into super stardom was almost played by another actor entirely. The same goes for many other iconic comic book characters over the ...