If Captain america flops, then the Marvel Avengers movie is pretty much doomed. I'm not even going out on a limb by saying this: do you think that Marvel's outlook on its future projectswould be so rosey if Iron Man had been a box office flop? Hell, no. Why do you think that Marvel was so determined to keep control of their slate of future movie projects dealing with some of their more iconic characters? They knew the score going in: if these films are not done right then the future of Marvel as a source of movie properties would be tarnished, so better to make sure that the movies that are going to be mad are made properly - ie that the creative reigns are held by those who know what needs to be kept in the picture to make it a successful movie for its initial target/intended audience of comic book fans who will be there first day and ready to spread positive buzz about a comicbook movie if given a half decent piece of filmmaking to work with.