My favourite is The Empire Strikes Back.
1) Episode 5
2) Episode 4
3) Episode 3
4) Episode 6
5) Episode 2
6) Episode 1
I love Empire Strikes Back, New Hope, Revenge of the Sith and Return of the Jedi. Attack of the Clones is pretty good. I'm not a fan of Phantom Menace.
EDIT: Revenge of the Sith because of the special effects and some of the secondary actors (though the acting in the original trilogy is much better). I agree that Hayden Christiansen is awful and needs to be shot out of a cannon as far away from Hollywood as humanly possible. That would be Tokyo, I think.