1. The Empire Strikes Back: Tight story telling. Great characterization. A sense of real drama. Great special effects that strengthen rather than distract from the story. The Imperial March! One of the best cliffhangers of all time.
2. A New Hope: This is the name of the movie. It's just one of six chapters in the Star Wars line up and was added after it was clear there could and would be sequels. It's funny, I like this largely for the nostalgia and one of the best endings in any film. The dog fight at the Death Star and the fantastic Williams score that accompanies it still has me at the edge of my seat when I watch it. Still, this is far behind TESB.
3. Attack of the Clones and The Phantom Menace are tied for third for me and just slightly under ANH. I like them for different reasons. TPM has a great name and there're are great hints of a good story that Lucas never gets around to telling. However, for sheer fun and excitement, this movie has a lot of it. It also features the best lightsabre duel to date. AotC, however, I like because there's another great story here cluttered under a lot of bad dialogue. Cut out the dialogue (particularly the horrible stuff between Padme and Anakin) and we have another good film.
5. Return of the Jedi: Like the two prequels, a lot of potential here marred by Ewoks and a very, very sappy ending. I'm all for good endings, but I like to see a price paid. The only price we get is Vader's demise, but it really doesn't seem right to me that a man responsible for the murders and deaths of millions is rewarded with an afterlife alongside Kenobi and Yoda even if he was "redeemed."