In the '90s, Marvel split their titles up into "families" for the film and licensing deals. These include all the heroes, villains and secondary characters most closely related to the title.
- Spider-man family, held by Sony
- X-Men family, owned by Fox (including all of the mutant titles and the name "mutant")
- Fantastic 4 family, owned by Fox (includes Silver Surfer and Galactus)
- Hulk family, sold to Universal, reverted to Marvel
- Daredevil family, sold to Fox, reverted to Marvel
- Avengers family, owned by Marvel
- Not sure if Ghost-Rider was sold as a family, but maybe
When they packaged the rights to sell to Universal, they were lumped by these families. Titles that fall completely outside of these families or that were newer, like GOTG and Big Hero 6, weren't included in the deal. But there are other weird factors, Universal Parks has certain control over the comic-book likenesses of these characters and the name Marvel at extends beyond their Orlando location.