The Original Trilogy
The original trilogy is, on the whole, better than the prequel. Each individual release in this trilogy is better than every individual release in the PT. In fact, I dislike the PT so much that I prefer to forget it's canon when I watch the originals.
1. The Empire Strikes Back
Easily the best Star Wars movie, and the only one I'd rank as a true work of art, a piece of great film. It's meticulously detailed--everything, right down to the camera work and the lighting, helps create a contemplative, sometimes despairing, sometimes uplifting atmosphere. The characters are at their peak here, the script is clever and witty but also sincere and sentimental. The Star Wars movies are character stories, and the arcs here are something to behold. Magnificent.
2. A New Hope
Perhaps the most well-executed Hero's Journey story in film history, but it never takes itself more seriously than it should. It has a youthful exuberance and enthusiasm about it which could not be manufactured--this all had to come naturally. Great adventure story, and it earned its place as a classic.
3. Return of the Jedi
There's a tiredness here, and you get the feeling that if its two predecessors hadn't been so good this story couldn't stand on its own. Yeah, that's kind of the point, though. It managed a good balance in tone between the first and second films and the story of the Rebellion and Luke's own personal journey both come to a satisfactory close. Not the best, probably couldn't stand on its own merits like the other two, but it's a worthy sequel.
The Prequel Trilogy
Why do these exist?
4. The Phantom Menace
This movie has a senseless, badly-constructed script entirely lacking in any sort of emotion at all. The story is without context and character arcs are practically nonexistent. The actors move through this blue-screen world with all the conviction of Lucas' background CGI robots and creatures, and the jokes are juvenile in the worst way possible. This movie is without charm.
But hey, at least it still kind of looks like a Star Wars film and has some kind of remotely interesting special effects. At least Tatooine set is believable. Darth Maul is kind of cool, even if he's as insignificant and stupid as everything else in this unnecessary film. And at least the movie is not usually blatantly offensive--acting's flat, not laughably bad yet.
5. Revenge of the Sith
I really get the feeling that George Lucas got input from a 12-year-old boy who'd read too many 90s comic books when making this movie. It's dark, dark, dark, but the bad things seem connected tenuously at best, so most of it just looks like random angst. Anakin's motives, a driving force in this story, are unrealistic for anything but a sociopath or psychopath (perhaps Anakin already was one- see Episode II). I bought into the hype for this crapfest initially, but by the time it came out on DVD I'd realized it didn't live up to the hype. On further observation, I have to wonder what anyone saw in it.
Simply being "dark" doesn't make for a good movie. Bad things happening doesn't make for believable character development. Silly platitudes from character's who've only paid lipservice to political movements are meaningless and laughable. Seriously, "this is how democracy dies...?" I thought the Republic wasn't a democracy or republic, just some weird oligarchy. That's all we've ever seen in these godforsaken scripts. Nothing makes sense in this world.
Episode 3 was the point where the prequel trilogy came crashing down. The whole thing was so contrived and deficient that it had to happen sooner or later. But I guess the sheer intensity of the bad things that happen to everyone in this movie kind of makes for an experience. It was fun to watch the Emperor trot around the set like he owned the place, so yeah, I'll watch this movie.
6. Attack of the Clones
A contrived, stupid love story. The acting was really, really bad. Also, how am I supposed to sympathize with these characters? Padme excuses small-scale genocide and basically laughs off Anakin's ambitions toward a dictatorship. The video game sequences, like the conveyor belt, certainly don't help.
I'm not wasting any more words on this atrocity.