The Hobbit part 1 by a mile over anything else. However, I am very much looking forward to The Avengers, Batman, and Spidey as well. I do think John Carter is going to be a sleeper film for huge success this year.
I haven't seen enough of the Hobbit yet to be much more excited for it. I still can't even figure out if its being cut up into 2 films or if the second film is some made up sequel I've heard rumors on