I've only seen a handful of 2012 films, so of the ones I've seen, these are the best and worst...
Best: The Impossible
I liked this so much I wouldn't mind seeing it again at the theatre, but I haven't seen Zero Dark Thirty, Lincoln, etc. so this is subject to change.
Worst: The Hunger Games
Forced to watch this against my better judgment and absolutely hated it. Like a mid-80's Doctor Who episode when that show was really tanking but with a big budget and without the Doctor showing up to at least make it slightly palatable. Would have much rather seen the Doctor arrive in the TARDIS, meet Katniss, learn what the game is and being disgusted by it, then she becomes his companion and the two win the game and defeat the bad guys through superior intellect and not senseless slaughter.
Speaking of which, apparently watching kids killing each other is now family entertainment since this film was such a blockbuster hit, but I have to ask, if our real world society enjoys this crap, then how are we any different than the decadent and heartless elites in the film who are enjoying the exact same thing? And then people want to blame shootings like the Newtown Massacre on the 2nd Ammendment while ignoring mental illness and irresponsible filmmaking such as this, which only serves to glorify violence and desensitize people to it. On a lighter note, was there anyone more annoying in film this year than Stanley Tucci was in this? Just brutal and distasteful from start to finish and one of the worst films I've ever seen.
Most Disappointing: The Dark Knight Rises
Anne Hathaway's Cat Woman was the best thing about it, after that there isn't a whole lot to recommend. Too long, lost interest and got bored half-way through, Bane was lame, too many stupid plot points to mention, etc. It's still a Nolan film, so it's not horrible, but it's also far from the greatness that was expected. Unlike the first two films of the trilogy, I never want to see this again.