And here's a shout-out to "and Sauron" for his defense of the Prequel Trilogy. I'll just add that Jar-Jar Binks, as annoying as he was, filled a Campbellian archetype (the fool), which George Lucas has professed an intentional concern for. His utility to the story as a whole is evidenced by the fact that Palpatine and his cronies are able to trick him into giving emergency powers to Chancellor Palpatine (the "dellow felegates" line). And I've heard a lot of people complain that the Anakin–Padmé romance was cheesy. Well, of course it was. Like "and Sauron" said, he'd been isolated in Jedi training and she's been caught up in politics for the last ten or so years. Sure they look like adults, but emotionally and romantically, he's still nine and she's still fourteen. Also, some of the deleted scenes shed additional light about why she ends up falling for him (family pressure and "lost-puppy syndrome").
My complaint about the original trilogy is that the dialogue, especially in Attack of the Clones, was overly didactic. I don't think there were any memorable lines from that film (please, correct me if I'm wrong).
To conclude, here is the order I esteem them in:
- The Empire Strikes Back
Revenge of the Sith
A New Hope
Return of the Jedi
The Phantom Menace
Attack of the Clones