Apparently Meli and I are in the minority amongst our friends as to the badness of Revenge of the Sith. Since our friends are all intelligent people with fine taste in movies, I began to wonder if I had missed something, if perhaps I was being too hard on the movie, and if I was focusing too much on the dialogue and not enough on the good stuff.
The order of the day with the Star Wars franchise has always been bad dialogue/good story. Harrison Ford's famous on-set outburst - "You can write this shit, George, but you can't say it" - applies throughout the Star Wars saga and was an acceptable flaw since the stories were so engaging. What was so disappointing about Revenge of the Sith was that the story stank as well. And what was really disappointing was that it stunk up other stories in the process of stinking itself up, namely the original movies.
Darth Vader didn't help the Emperor hunt down and kill the Jedi. He shot a bunch of fish in a barrel while the other Jedi were ambushed by the storm troopers they were commanding. Obi-Wan's description of the Emperor's campaign against the Jedi created (at least for me) a sense that as the Republic fell the Jedi scattered throughout the galaxy and were systematically hunted down over some prolonged period of time. Under the facts of Revenge of the Sith, the Jedi were wiped out in a single afternoon. And Anakin was only tangentially involved.
Anakin wasn't seduced by the Dark Side. He crossed over because he wanted to keep his wife from dying and he was mad at the Jedi for not letting him join the Popular Kids Club. Obi-Wan had a tougher time convincing Luke to become a Jedi than Palpatine had convincing Anakin to kill the Jedi. Very disappointing.
As I mentioned in an earlier comment, the scene where Luke asks Leia about her (and his) mother is meaningless now. Leia never knew her actual mother, which was probably a good thing since the engaging, proactive, and intelligent woman that Leia became obviously had nothing to do with her biological mother, who spends this entire movie being pregnant and staring out the window (Meli's observation, not mine).
(Meli adds: Somehow feminism passed Padme by in the 00s when our hunger for strong female characters is at a peak, while Leia was a poster child for Ms. Magazine at the height of the Reagan Era. Also, falling in love was incidental to the story of Leia's life, where it was the quintessential (and only) achievement of Padme's.)
These are just a few of the ways in which Revenge of the Sith gutted the original series. The groundwork for the fall of the Republic that was laid in Episodes I and II was great - a Sith Lord masquerading as a Senator orchestrates a civil war in which he is secretly controlling both sides, creating enough chaos to reduce the Republic to a totalitarian state. Where Lucas dropped the ball was in the characters. Darth Vader was always my favorite movie character growing up - not just my favorite Star Wars character, not just my favorite movie villain, but my favorite character - so I had special expectations when the prequels began and purported to tell the tale of how Anakin Skywalker became Darth Vader.
Essentially, the prequels are not about the Darth Vader of A New Hope, The Empire Strikes Back, and the better parts of Return of the Jedi. Prequel Vader is not the ambitious and ferocious warrior who seeks power for the sake of power and destroys his enemies with ruthless efficiency.
Rather, he's a sniveling sidekick - first to Obi-Wan, then to Palpatine. He's not the Vader who lays waste to the incompetent military leaders in the beginning of The Empire Strikes Back. He's the lapdog who lurks next to Palpatine, hanging his head and keeping quiet, until the Emperor orders him to start defending him from Luke at the end of Return of the Jedi. Prequel Vader has no will of his own. He has no greatness, good or evil. So we don't care that he goes from good to evil (and back to good). These aren't his decisions. He's just being manipulated by his circumstances. Just like Padme. (Meli adds: God knows how she got pregnant, since neither of them could be counted on to make the first move toward having sex.)
So I guess that's why I hated Revenge of the Sith. It wasn't just a poorly acted, poorly written, and poorly executed movie about a bunch of uninteresting characters (with the exception of Palpatine, who as the only shining star of the movie, moreso because of the acting than the writing). It was a crappy movie that sterilized quality characters in other quality films. And that's why I now refuse to acknowledge the prequels as part of the official Star Wars universe. They are, as Sean said and as I quoted before, elaborate (and crappy) fanfiction that happened to be written by George Lucas.