Gary Busey does not have the same kind of clout Mel Gibson has. Busey is already thought of as a joke....
Billy Zane was in the movie with him. Both had starring roles at one point in their career.
Gary Busey played the main villain in the first Lethal Weapon film (1987) with Mel Gibson.
He still has a viable career even if not as a lead actor.
http://www.imdb.com/name/nm0000997/
John Travolta had peaks and valleys in his career too:
http://www.imdb.com/name/nm0000237/