With the announcement of 'Batman vs Superman' or whatever the official title will be, I think Hollywood is slowly but surely opening the doors or possibly the "Flood Gates" For future match-ups that won't only involve heroes vs villains, but now will showcase what would happen if two heroes don't see eye to eye. Which historically isn't something new to the world of comic books, but could make for some interesting films in the relatively near future.
They teased it already in 'The Avengers' With Hulk and Thor going at it in the Helicarrier. But some day we may see some DC/Marvel crossovers. I understand that some heroes are just too powerful for others. But there is always a way to level the playing field. Who would you like to see go toe to toe in future hero films?