I would like DC to make a revamped version of the Justice League, but this time as a prequel to Young Justice using the adult justice league characters. (Batman, superman, wonder woman etc).
Marvel wise, an animated young avengers show with Spiderman and some others would be cool.
Arthas. There’s way too much story for a movie (they had this problem with the Warcraft movie already). It could have a five season run easily, and lead to so many spinoffs.