Some people have hated the times when the world's biggest superhero companies have crossed over with each other. Me? I've always loved DC vs. Marvel events. It's a shame nothing like, say, Superman vs. Spider-Man will almost certainly ever happen on movie or TV screens.
Superhero movies cost too much for anything like a movie teased by Alex Luthor's insane mash-up trailer to ever manifest for real. You've got to love the little touches like the kryptonite-green filter in the shot where Iron Man blasts Superman. Like most good fan or pro crossovers, it puts your brain into overdrive as to which heroes could win in what scenario. Green Arrow vs. Hawkeye? Hulk vs. Wonder Woman? Depends on who's writing.