Jim Carrey? No. Adrian Brody is a fantastic actor, but may be too soft-spoken for this role. I'm not sure he has the energy needed for this kind of role. Lachy Hulme, must be the best actor we've ever seen in some way. Otherwise, I'm just not seeing it. Steve Buscemi is more the Scarecrow type. Crispin Glover has the look, but the man has never impressed me as an actor. He's always very broad in his performances, and never really nails anything down, in what I've seen him in. Tim Roth? A good actor, not Joker material. Ditto Alan Cumming.
Honestly, for a sequel, given that you had Liam Neeson in BATMAN BEGINS, I think you're going to need a "name" in the role of The Joker. I think you need Jude Law or Johnny Depp. And I think either of them would excell in the role. As far as Joker goes, you don't need somone who can be spastic and funny. The Joker's real impact comes from when all that falls away from him, and you see what he truly is: and what he truly is, is not funny at all. And Jude Law and Depp are the two men who, I think, can best portray this aspect of The Joker, and make him more than what's on the page.