I haven't seen either of the Hobbit films yet, but I've watched all of the LOTR movies multiple times. Because I'm a Tolkien nerd. I plan on back-to-backing the two hobbit films at some point, because, again, nerd.
Hobbit cartoon is great.
I think that Return of the King is the best film of the three I've seen, as it plays most strongly into what peter jackson's good at--the visual effects and has already gone past what he's not so good at--the storytelling.