I actually liked Ewen McGregor as the younger Obi Wan, and I felt like this is the first time that character had convincing emotions of the three. I felt a stirring in his emotional farewell after he had defeated Anakin. The guy who plays Palpatine (forget his name) does a good job portraying a creepy emperor, of course he was in the original movies.

I don't really blame the actors that much, I blame more the script and Lucas's directing.