Diego said:

In my opinion, Episodes II & III, suffered a loss in quality in both performance, dialogue and direction compared to Episode I. Not that Ep. I was that great to begin with though. Maybe it was the exagerated use of blue screen.

Idunnoman.

Padme wasn't COMPLETELY monotone in those two movies, as she was in I, McGregor was kinda alive and sarcastic and pretty much the same (a nice, even if terribly understated performance by him overall), other than that, um... who else made it into the sequels anyway?

CGI Yoda was obviously leaps above that silly puppet from I (and even more expressive than the puppet from the OT, although the performance itself was too kitschy and over-expressive, like "look, I'm smart and think a lot", and the voice acting too much of an annoying cartoon saying clichéd lines in backwards grammer), and Sam Jackson had exactly two memorable moments in I and III:

In I he kinda looked gloomily at Yoda, in III, his angry face at Palpatine. Also, at one point in I, he inexplicably gives off that glare of threat from Jackie Brown, where he tells Melanie to go answer the phone :DD

Everything else looked like he was on sometiens during shooting.