I think it depends on how rich the world, the lore, the story etc for it to convince me into thinking that I'd want to play this if it were to become a game. If I were to pick, then I'd say that books/manga have a better chance to become games since they can be as long as they need to be. Movies can do this, but in the space of two hours, TV/anime can be another good option, and I'm too dense to think of what else there is