The Avengers is taking 4 separate movie franchises (Iron Man, Hulk, Thor, and Captain America) and combining them all into one huge movie with all the main characters from each movie.
Doing some preliminary research, I have not found anything in cinema history that has been attempted like this before (however in other media like comics, TV, literature, it seems it has).
My question is simply, is this the first movie to attempt a major crossover of cinema franchises? If not, what was the first movie to accomplish this? What was the success of this movie (sales, overall critic/public opinion)? And what were the franchises that it combined?