I was going to say all of them, but like a lot of people was not a big fan of Phantom Menace. It was okay, but definitely the worst of the 6. I like the original trilogy over the prequels, and while I think that story and cinematography-wise Empire is a better film, I have a soft spot in my heart for A New Hope. My favorite score though is Return of the Jedi, especially the battle in the throne room. Attack of the Clones was a good film that definitely got us back towards the feel of the original trilogy (and I nearly had an orgasm when Yoda ignited his lightsaber and fought Dooku). Revenge of the Sith had great action and by far the best lightsaber battles. Great topic.
May the fourth be with you!