I saw on Pawn Stars a drawing made by Marvel and DC about a crossover of Spiderman and Batman. At the time in the early 90's Marvel was struggling and so was DC, comic book sales sucked. Fast forward now and it would be awesome if we could have Hulk vs. Superman or shit like that. Sadly licenses will mess that up. I did read that Sony and Marvel came to an agreement with Spiderman and now he can join the potential 3rd Avengers movie which is probably why they are rebooted Spiderman again with a new actor. Fox is the only holdout and are being pricks about X-Men so marvel vowed to stop making X-Men comics and characters because Fox had first right to sue them each time. They are forcing their hands.
One of the most epic comics I ever read was Hulk vs. Wolverine. That would be a killer movie.