Let me begin by saying that I am all for a shared universe. I love seeing my favorite superheroes showing up in each other's comic books and I think that Marvel is doing something truly unique with the idea of all their superheroe movies currently leading in The Avengers. And yes, i was one of millions of fans who was dissapointed when DC announced it would not follow the same path.
However as much as I like what Marvel is doing, I have to realistic and ask how much longer can this experiment go on? Like it or not, when the latest Batman or Iron Man movie comes out, we the fans are not the only ones who go to see it. A big portion of the audience are the general public, who are just looking for a good movie to watch for 2 hours. A lot of these people are probably not aware that Marvel is tying their films together for The Avengers and frankly, some may not care. Some people just want to go in and watch a story about Iron Man, and not be bothered with a lead in sequence to Thor. The reaction to Iron Man 2 was proof of this.
I can also imagine that this initiative places a strain on the director of each of these movie. Even if Marvel does not mean to or does not think it is, telling a director to tie thier movie to a pre exhisting vision puts a damper on creativity in some ways.
Plus what happens when the actors get too old or stop being interested. Does that mean we go back and reboot everything and start all over tying stuff together? In a perfect world, I would keep these characters young by using digital verions of the actors, and let the actors do voice work and some mo-cap. And if you try to recast Robert Downey Jr, well I can not see anyone exepting that idea. I've heard Charlie Sheen's name thrown around, but he's no Tony Stark to me.
We also know that Shane Black's Iron Man 3 will take place after The Avengers and that he is planning on focusing the story around Iron Man. I can only imagine that the other heroes will be treated in the same way. And post Avengers, thats an acceptable idea because the pressure of setting up something huge will be off.
Once again, dont get me wrong. I love the idea of taking a page from the comics with a shared universe,and I think it is worth a try, but its a big burden for Marvel to bare.