Which comic book character would you like to see on the silver screen? Who would you cast to play the role?
This is one of those questions that really deserves an "in an ideal universe" or "under practical circumstances" modifier, because that really does make a difference.
For example, in an ideal universe, I'd love to see the Authority get the treatment that the Avengers movie is getting right now, with a series of lead-up movies. You've have your Jenny Sparks: Spirit of the 20th Century nostalgia piece a la the Captain America movie; the gritty, urban, tormented-male-lead Jack Hawksmoor: King of Cities movie; a Midnighter and Apollo movie about gay fugitive superheroes seeking revenge with flashbacks to the destruction of their team and the reason they're out for said revenge; and maybe even a Stormwatch movie tying some of the threads together before you got the proper Authority movie. (Much as I love Angie, her origin does not a movie by itself make*; nor does Shen or the Doctor's. Plus, a Jeroen origin-story-movie would be a little too Trainspotting for most people's tastes.) And in this ideal universe, I would cast Daniel Craig as Midnighter (azarias's idea) and Hrithik Roshan (six photos here; I could not pick) as Apollo, although I seldom fantasy-cast so thus ends my thoughts there.
In a practical sense, if I heard they were actually making an Authority movie or even a series of Authority movies or even just the Jenny Sparks movie, I would pale and start building a fallout shelter immediately. The Authority is pretty high on the list of topics I feel Hollywood would mutilate. And on a smaller note, while Daniel Craig as Midnighter actually isn't too completely far-fetched, Hrithik Roshan as Apollo is never going to happen.
However, still talking in practical terms, I, like many other people, have spent most of my time since the abortive Wonder Woman project going "Why didn't they just make a She-Hulk movie? I mean, everything they were describing that made no sense for Wonder Woman--the dual identities and their conflict, the eating ice cream and crying over men, the media influences, the Ally McBeal homages--all of those are Shulkie. But I have no idea who I'd cast to play her. Probably not the Hollywood-skinny type who would be bound to get it. (Personally, I cast Bipasha Basu for Wonder Woman--Bollywood has a remarkable number of actors and actresses who actually look like superheroes--but again, that abortive Wonder Woman project makes me think that an actual movie about her is still ideal-universe, not practical-universe.)
Also in the ideal universe, I'd love a JLI/Can't Believe it's Not the Justice League comedy/action movie, but again, with what Hollywood is putting out right now I just can't believe it would do well.
And I would love a really well-done Batgirl movie, or even just to have her inserted into the current ones--I think any Batgirl would adapt much better than the Robins to the Nolan-verse--but failing that, some time with Joel Schumacher and some very pointy heels would be equally therapeutic.
* What I would do is make Angie's backstory the trailer opening: you see a girl go to her high school guidance counselor and get asked, very bored, "And what are your plans post-graduation, Angela?" and she goes, "I'm going to be a superhero," and the counselor smiles, very clearly pained, and says something about how she's got some very nice pamphlets here for pre-med. And you see wee!Angie's eyes narrow, and then it cuts to some explosions and adult!Angie standing there in all her CGI chrome Engineer glory having just caused the explosions. Then you get snippits of the other characters. Never gonna happen in the real world, because of course everybody knows women can't be hooks for superhero movies unless they're being sexy.