I'm pretty sure Marvel gets a % of the gross, otherwise whoever made those deals needs to be sacked.
What i'm more interested in finding out though, is the length of the contracts. At the moment it's:
Fox: X-Men, Fantastic Four, Daredevil, Elektra
Sony: Spider-Man, Ghost Rider
Marvel got back the rights to Hulk and Punisher. The two i'm unsure about are Blade (New Line) and Man-Thing (Lions Gate).
What i really want to know is if the contracts are ongoing for as long as those studio's keep making movies based on the characters or if they have a time limit.
I remember reading in Wizard magazine back in the late 90's when all these movie rights were being sold by Marvel that Marvel had signed 20 year contracts with the studio's. If that's the case then rights will start to revert back to Marvel by the end of the decade (X-Men was in 2000, the contract was probably signed a couple of years before that).
I just wish this info was available, been wanting to know this ever since Iron Man was released. Maybe SHH can ask Kevin Feige for the details next time they speak to him.