I like the suggestion io9 made earlier today (which is similar to one I've been making for years:
Where Is Our Wonder Woman Smallville?
I also think
Gotham Central would be a natural for TV adaptation, a police procedural dealing peripherally with superheroes and supervillains. I've never actually read it, but the idea seems like something TV executives would eat up.
Although I'd kind of like to see a
Smallville spinoff where J'onn J'onnz heads up an SCU team. Because Phil Morris deserves his own series. Or they could spin off Sarinda Swan into a
Zatanna series -- so long as Paul Dini wrote and produced.
Of Marvel characters, I agree Daredevil would be a good choice. I rather liked the '90s TV movie
The Trial of the Incredible Hulk, which was really a backdoor pilot for a Daredevil show. Aside from making DD's costume less devilish (black, no horns) and having a Kingpin with hair (John Rhys-Davies, fully bearded), it was a pretty faithful translation and worked fairly well.