The prequel that I have seen the least, and also probably the worst in my eyes. Literally nothing happens in this film, and I was bored the entire time.
Maybe it was trilogy fatigue, but I pretty much hate every character in this. It is not like I ever liked the character Anakin, but he is easily at his worst here. His flip flopping between whether he should be good or bad is excruciating, and the amount of complaining he does is at an all time high. At least in the second film there is a little variety as he has to deal with his feelings for Padme, however horrible that might be to watch.
Speaking of Padme, her character is reduced to the dutiful wife in the film, and I couldn't stand it. At least in Clones she is a kind of strong character, and she looks rather fetching in her outfits. Lucas totally uglified her character in this the third film, which I interpreted as Lucas saying that once a woman is married she has no worth anymore. Lucas is a total feminist apparently. He is all about the single ladies.
By far the worst character though is Palpatine/Darth Sidious/Scrotum Face. It honestly feels like the entire movie is just Palpatine telling stories and people being way too stupid to figure out that he is the bad guy. I hate everything this guy has to say, as much as I hate his stupid face.
Apart from the Order 66 scene, I find no redeeming qualities in this film. There isn't one memorable action set piece, and no one better comment about the stupid lava planet lightsaber battle. Apart from the fact that Anakin gets lit on fire at the end of the battle, there is nothing I like about this fight scene. I also hate everything about General Grievous and the ridiculous lizard chase scene.
While I actually had a decent enough time rewatching the first two prequels, Revenge of the Sith was just a chore to get through.