Forget about the whole licence debate between Marvel and Fox and assume that Marvel has rights to everyone.
Villains:
Doctor Doom, Galactus, Magneto, Sentenals, Apocolypse, Taskmaster, Venom, Carnage, Doctor Octopus, M.O.D.O.K., Green Goblin, Mystique, all of the major Brotherhood of Mutants.
Heroes:
All the X-Men, the Fantastic Four, Silver Surfer, Blade, Moon Knight, Nova, Deadpool, Namor.
I'd like to see the X-Men be turned into a tv show. However, I'd like to see the Fantastic Four in a movie (that's actually good and have Doctor Doom be the villain for their first film as well as the following Avenger's movie. The post credits for that Avenger's film could be Silver Surfer scouting Earth for Galactus' next meal, since we're gonna need a new "big bad" after Thanos. As for Moon Knight and Blade, my idea is an anti-hero Defenders team staring Punisher, Ghost Rider, Moon Knight, and Blade all fighting Taskmaster. Venom and Carnage could be easily done. As we know Spider-Man will be in Infinity War. From what I've heard, it will take place mostly in space. If that's the case, Spider-Man could bring back the Symbiote. Spider-Man Homecoming 2 could be him fighting Venom, and half way through when Eddie gets thrown in jail and the Symbiote brakes him out, some bit of it latches on to his cell mate, and then Carnage is born. Spider-Man and Venom would have to team for a bit and fight Carnage. Not sure how they'd go about Green Goblin, Doc Ock, or M.O.D.O.K. Nova could partner with the Gaurdians of the Galaxy for his first apperance and Namor could have a Netflix show. Deadpool would be within the X-Men tv show.
Did I miss anyone?