Well, I enjoyed the flick and felt it was the best of the prequel trilogy and maybe even the best SW movie since TESB. I felt the dialogue and acting was better than I and II and pretty much on par with the OT. I thought Ewan McGregor as Obi-wan Kenobi and Ian McDiarmid as Palpatine were particularly noteworthy. Remember that the SW series has never really been a bastion of great acting and I accepted that long ago. Frankly, I blame the inadequacies of Ep.III on I and II. It felt rushed because, frankly, some of the stuff that happened in it should've occured in I and II. If we could go back and redo the prequels, I would take what we have now and modify it in some key areas.
Some futile, revisionist, geekly, nut-shell suggestions in no particular order:
I would've started Ep.I with Obi-wan as he appears in Ep. III and Anakin as an adult (either as Kenobi's apprentice or as an established Jedi). I don't think many people really cared how Anakin was "discovered", but maybe it could be briefly mentioned in the opening crawl. Just mention that he was trained later than normal, is restless, and blah. Somehow introduce Padme and start the beginnings of her and Anakin's little forbidden romance. Palpatine is either already in power, or is elected into it. Qui-gon is either a contemporary of Kenobi's or not in it at all. He doesn't really matter. Anakin and Obi-wan defeat Darth Maul, but probably under different circumstances. The Clone Wars are already on (also explained in the opening) and Obi-wan and Anakin have rip-roaring adventures. Jar Jar is nowhere to be seen. Anakin does disturbing things that foreshadow his fate, subtly spurred on by Palpatine.
Ep.II is 2-3 years later and the whole secret romance thing goes into high-swing. Luke and Leia's conception is implied (a sex scene in Star Wars? Yeah right...
) The Clone Wars continue. Anakin and Obi-wan continue to have swashbuckling adventures and ripping good fun. Still unknown to Obi-wan, Anakin does more bad, irrational things and is continued to be manipulated by Palpatine. Anakin completes his turn to the dark side, begun in Ep.I, in a cliffhanger, downer ending similar to TESB. Palpatine also reveals himself for what he is at some point too.
Ep.III is maybe a year or so later and is similar to what we already have in some respects. Luke and Leia are infants, but are hidden at the movie's end. General Grievous shows up (or he could do so in Ep.II, really). Grievous turns out in a plot twist to be a "resurrected" Darth Maul in a final duel with Kenobi. The Clones have turned "bad" and the Jedi have been persecuted since Anakin became Vader. Anakin now wears a "Vader-ish" suit, but without the helmet or the eletronics. The Jedi have greatly suffered and been diminished. Obi-wan spends most of the movie trying to track down Anakin and redeem him. After a few fleeting encounters, the final duel eventually ensues and the rest is history.
There are all kinds of details, subplots, and characters that were left out, but I think if Lucas had followed a similar outline, the Prequels might've been more popular.