I have been known to bore people to tears at parties with a two-hour speech about how the prequels could have been better. Recently, though I find myself agreeing with Gaff - I don't care anymore and just want to walk away. However, here are a few main points I'd have liked to see different (in no particular order):

1) Anakin in TPM is the same age as Luke was in ANH
2) Yoda is Obi-Wan's master (not Qui-Gon)
3) no midichlorians
4) Anakin does not come from Tatooine
5) In fact, Tatooine doesn't appear but Alderaan is a prominent planet in the series
6) the story begins with the droids, who are already together, we do not see their "origins" and Threepio is NOT built by Anakin!