It's not that "ROTS" (unfortunate acronym--) is a BAD movie--it's really not. It's just that seeing it, on the one hand, you realize that the three "first" movies taken together have about enough plot for one long movie, and, on the other hand, Anakin still falls to the dark side too quickly. OK, he really isn't starting off his career as a bad guy with a slaughter of the innocents; he's already done that once with the Sandpeople village, but the movie doesn't really point up that connection, which is a weakness.
Roles and acting level are much the same as the other two films of this sequence, and I suspect most readers already have opinions about those things.
Some of the things that pleased me most were the small things: Bale Organa’s starship is the same one that appears as the “blockade runner” at the beginning of “Episode 4”; in a closing vignette of the Death Star’s early construction, the distinctive image of the late Peter Cushing (Grand Moff Tarkin) appears. The reconstructed Darth Vader breaking the restraints of this operating table like Frankenstein’s monster--. There were some interesting bits done to reconcile plot inconsistencies, such as Senator Organa casually ordering C-3PO brainwiped so that he doesn’t know that Leia is adopted or has a brother. On the other hand, it still leaves some awkward connections: why would Yoda make the cryptic “there is another” remark at the end of “The Empire Strikes Back” since both he and Obi-wan (and the audience, if they had seen the films in “order’) know very well who the “other” is.
I have to agree with some other writers who opine that the Jedi have in part brought disaster upon themselves through decadence, arrogance, and complacency. Only when it is too late do any of them begin to wonder what “bringing balance to the Force” might really mean when the Jedi have been on top for so long. I’m not sure if it was intentional, but Obi-wan’s failure to kill Anakin cleanly is an act of either cowardice or spite that will of course come back to haunt him. Ironically, the film ends with two Sith and two Jedi—balance, indeed.