You'd have to split it up in my opinion since I don't think any one studio could afford rights to the entire Marvel universe. I am sure WB/DC had their deal in place for a while. With Marvel movies becoming so big these days you'd definitely have to split it up. So I'd go:
Fox: X-Men (Just for the fact that Marvel can not take it back... and the mutant universe could essentialy be independent from the rest of the Marvel universe due to the unlimited potential on its own.)
Paramount: Iron Man, Thor, Cap. (Give them all major and most minor Avengers characters)
Universal: Hulk, Fantastic Four, Dr. Strange, Namor (Sort of the paranormal, too strong for this world type heroes that can blend well amongst one another)
Sony: Spiderman (No need crossing Spidey over into other franchises. He could easily hold six if not nine films by himself)
Independent/Non-major studios: Heroes for Hire, Dare Devil, Black Panther, Punisher, Black Widow, etc
Disney: Family oriented, animated type Marvel films.