I'd love to see a TV-show based on Neil Gaiman's "Sandman", but only if it's true to the comic, and since most of the comic-movies or -series aren't, I'd rather pass on that one. But it would have great potential and could spawn so many spinoffs: Death, Lucifer, Books of Magic, even Hellblazer (f*ck the movie).

I love the nod to Gaiman's "Death" in Supernatural (Season 2, Episode 1 "In My Time of Dying").

Another comic book based series I'd like to see would be Bill Willingham's "Fables".