The acting was pretty bad, but of course it was predictable. It was supposed to be predictable. Ep I stunk, but he felt he had to explain Anakin so it worked for him. Ep II wasn't that bad and Ep III can go against the original III. Everyone knew he turned into Darth Vader and that Palpatine was the the Sith so there was no getting around predictable. Titanic was predictable too, but a lot of people seemed to love that movie.
I think the problem that a lot of us ran into was that we saw the films as kids and no matter what he did with the last 3 it would not live up to our expectations. We were much easier to impress when we were children too. I wonder if these movies were made the other way around, meaning we all saw the Anakin Episodes when we were younger instead, what we would all think.
I've probably seen every documentary on Star Wars and Empire of Dreams is probably the best one. He took a huge financial risk with that movie.