"Lucas, on the other hand, probably told his actors exactly how to perform. Most actors look less wooden improvising than these guys did on script."
I think you're dead wrong. Everything I've EVER heard about Lucas the director is that he gives virtually NO feedback to his actors. He's a fantastic editor, and a superb post-production director (the guy has an uncanny sens of pacing, timing, and delivery when he directs animators), no matter what the current trend of easy-target vitriol says, a creative genious, and a brilliant businessman, but he's a mediocre director of actors. Couple that with throwing actors into an almost entiely bluescreen environment where they probably have no real idea as to where they are, and what they are supposed to be doing, and I think you end up with something that looks like Phantom Menace. I think the real problem with the performances in TPM is that the actors were lost in an invisible world, and ladden with shit for dialogue.