Disney bought Marvel after Iron Man and Incredible Hulk. Incredible Hulk was key in that it showed Marvel didn't just have a one hit wonder film property on its hands. It proved it could do it again with Incredible Hulk. Not a fantastic hit like Iron Man but good enough for Disney to pull the trigger on a $4 bil buy out.
Similarly, Cowboys & Aliens, which is doing similar to Incredible Hulk, is a good start. It's not MIB, but it's a good start for PDOS' first summer event movie. Impressive that it is approaching Hulk numbers in that it is new property.