People who know Marvel Comics will know that some characters from the comics and the stories in them do not appear in the movies at all. I'm sure you've been wondering why, haven't you? There are licensing problems and I'll try to explain them to you in these articles.
With the Marvel Cinematic Universe Marvel has created something that has never existed before. A huge success machinery that will definitely continue to work for years to come. But again and again the Marvel Studios have to fight with the fact that not all rights belong to them at the own Marvel figures.
What is the reason? Back in the 80's and 90's, comic sales generally went down rapidly, the comic era came to an end because children and people preferred to watch cartoons and movies rather than read comics, and that's why Marvel wanted to get rid of the rights to all the heroes for film adaptions because there weren't any Marvel Studios at that time like today that did everything themselves.
So for example Sony approached the Marvel Comics and wanted the license for Spider-Man, that means they wanted the character. Spider-Man, but also all the other characters that appear in the Spider-Man comics for themselves and for future movies. Marvel had promised Sony at that time the licences for and also made the suggestion to get Iron Man, Hulk and all other heroes as a package for 25 million US-dollars. Sony only wanted Spider-Man at that time, Marvel then sold Spider-Man, so the rights to the character and all other characters in the Spider-Man comics, for future movies and series.
Then there were sold the X-Men to 20th Century Fox, then the Fantastic Four to Bernd Eichinger and there were also sales from the Ghost Rider or Blade and so on. Most heroes have a successful film history behind them as you know.
And with such a sale of rights we have to speak of two kinds of legal assignments. One is production rights and the other is distribution rights. Of course, the production right says that the owner is the sole owner of the right to make a film about this particular character or a series or a video game. The distribution rights say that perhaps another studio makes a Hulk film but only this studio with the distribution rights may distribute the films.
That is, if Marvel were to make a Hulk film now and the production company that has the distribution rights says no, we don't want that, then the film would no longer be worth it, because then it would not be allowed to be sold. That means again, even if the film were to be produced, it would not be allowed to be shown in cinemas, released on DVDs or Blu-rays, or on TV because the distribution rights provide for that.
I hope that you can understand both now, because we need that to understand how the legal situation is with the individual characters. The rights of most Marvel characters are still with Marvel Studios or Marvel Comics. But there are exceptions.