Even Deadpool already appeared in X-men Origins: Wolverine, I believe they didn't do him justice, it was lame to be honest. I'd love to see the true-to-the-comics Deadpool on the Big-Screen. That'd be awesome.
The Sandman series is my favorite graphic novel series (and quite possibly my favorite piece of writing), but I don't think it would adapt well into a series of movies or shows or whatever. The only way that I would be okay with it is if Neil Gaiman himself was fully involved in the adaptations. I would be way too afraid of other people completely wrecking the story, or losing the integrity of the works.
It's funny that we're talking about this. I actually attended a forum of panelists tonight (it was called Vision & Brilliance, hosted by The Connecticut Forum if you want to look it up) and Neil Gaiman was one of the speakers. At the end, they were taking questions and one of them was "would you like a Sandman film" (or something along those lines), and to condense his answer, he said no. He stated that he's seen a few scripts floating around of a film adaptation and they were all horrible (so much so that he said for one of them, he stopped reading after page 5).
I think Doctor Strange only had one animated movie (straight to DVD or TV special, methinks) and that was it. It'd be nice to see him all badass-ified in a live-action movie if it was done right. Not to say he isn't a badass already.
Zatanna could use some time in the limelight too. Young Justice and JLU weren't kind enough to her, constantly putting her as a side character.
Personally I didn't find his appearances in Teen Titans very interesting. He was very watered down. I have seen him in Young Justice, but still feel like he deserves something a little more interesting. At the moment I prefer him in his comic appearances like the scene in Identity Crisis when he takes out Elongated Man, Zatanna, Green Arrow, Black Canary, Hawkman, the Atom and would have probably dominated a Green Lantern ring using his own willpower if he'd had a few more moments. He also had a crossover with Marvel and fought Wolverine to a standstill. Personally I think he needs a bit more recognition than he seems to get.