Originally Posted by sabetoonth
Unless Ghost Rider's rights have reverted he's at Fox (I think its Fox)
But neither GR movie has a character officially named "Mephisto." Peter Fonda played the more traditionally-named "Mephistopheles" in the first GR film, so the comic-book character could belong to any studio at this point --- we have know way of knowing.
It's also worth pointing out that in the Infinity Gauntlet saga, Mephisto plays the role that "The Other" does in the Avengers movie --- i.e., Thanos' herald/mouthpiece.