I don't agree with you on this one. I saw Memento at the theaters, and loved it on the very first viewing. Obviously, I wanted to rewatch it so that I could understand the film in a new way, and I did--at the theater even! But it worked on the first time around because it succeeded as a film, on its own merits, telling its story in its way. Other films work this way, like some of those from Kubrick, Kurosawa, the Coen Bros., Cronenberg, Polanski. You don't get all that there is to get on first viewing, but you can recognize that they are great films. I'm not saying Avengers was a mess or garbage. I thought it was good. But it's not going to be great if a seasoned filmgoer can't appreciate it on a single viewing, or anticipate that it might be great, and is worthy of rewatching on a single viewing. It's not just about being able to better understand all that's going on, because no matter how many times you rewatch it a movie, certain aspects of filmmaking, and really storytelling aren't going to change. If you don't "get something," then there is definitely the opportunity to later appreciate it (this was the case for me with the Big Lebowski, Chinatown, even Pulp Fiction when I first saw it). But that's not the case here.