The acting: Wooden. Wooden like Pinocchio's nose. Wooden like Ishmael's leg. Not just from one or two actors, EVERYBODY is solid... fucking... wood. Except for when they're half-rotted particle board. Samuel fucking Jackson is dead flat, man. How do you even do that?!
The plot: Forced. Rushed. More sparse than a "Connect the Dots" drawing without the lines drawn in yet. "Oh... gee... I just killed a Jedi Master. Oh well, I swear to be a Sith, I swear to be evil and stuff. Yay, I'm on the Dark Side now." SIGH.
The theme: I would say "undeveloped", but really, at this point it would be more accurate to say "... there was a theme?"
The fighting: God, dear god, WHY did they not keep hiring Ray Parks as choreographer even if they killed off his goddamn character in the first one? This was baaaaaad - the fight choreography was actually better in the FIRST trilogy than it was in Episode III. And that's... really, really saying something. I dearly loved the first trilogy, but not because of virtuoso hand-to-hand fight choreography...
The CGI: for the love of Ghod, EVEN THE FUCKING CGI WAS BAD. There is one scene where Obi-Wan is standing next to an incredibly annoying chirping dragon steed thing that he's been riding, and not only does it look so obviously blue-screened that you're wondering if you've time-warped back to the 80's, the lighting angle is different between the glare on Obi-Wan's forehead and the scales of the dragontweetywhatsitthing. I GET BETTER PHOTOSHOP THAN THAT FOR FREE ON THE INTERNET!