Also, lets not forget that the Marvel superheroes are enduring characters that have been popular for decades and have been successful across multiple different media. Everyone knows who Spider-Man, Iron Man, and even Thor are; the same cannot be said of Kevin Flynn or Alan Bradley.
Sure, Disney's actively persuing another TRON film (a fact I'm very happy about) but TRON will always belong to a more niche audience. Even if Marvel can't work out a contract for Robert Downey, Jr. to reprise his role in a fourth Iron Man film, he's almost certain to return to the role in Avengers 2 and 3.
Marvel characters are here to stay, to deny that they're an enduring part of pop culture is foolish.