For me personally, the prequels officially sucked with Episode III right about the turn of Anakin to Darth Vader was where the whole thing fell apart.
I actually was a PT defender for TPM & AOTC, even though I knew they were flawed films. Of course in 1999 I knew Jar Jar sucked, and Jake Lloyd was annoying, and in 2002, I knew that the romance sucked, those were pretty much a given even among diehard SW fans.
I defended Lucas cause I actually liked where the PT story/Anakin story was going heading into Episode III. I understood his motivations in Episode II for killing the tuskens, they just killed him mom, so there was a revenge factor a person could sympathize with. Would I have done that? Definitely not, but I could understand someone losing a parent and going apeshit/
As the ending montage of AOTC played out on screen, I was juiced for Episode III. Just look at the last images: Dooku meets with Palpatine and the Clone Wars have begun. Yoda, Windu, and Obiwan debating where this is all headed to. Palpatine watching as the Empire has offically begun its rule and nobody knows it. And Anakin & Padme are secretly married as he takes her hand with his robotic hand. Great ending!
Episode III starts off with a bang, and then it all falls apart when Anakin decides to turn to the darkside, in what is one of the DUMBEST plot points ever, and one of the quickest turns to evil in the history of movies! He has a dream of Padme dying so he then trusts the man who was behind the whole war and the man who was killing all those jedi, and teh man behind the killing of his future wife in Episode II????? He turns within seconds, and then goes on a killing spree? Where is the motivation, where is the audience suppose to question to themselves, "Would I do this??" like I did in Episode II after Anakin killed the tuskens.
The whole second half of ROTS is ridiculous, is a montage of everything Lucas couldn't fit in the first 2 1/2 movies, and it goes from what could have been a good ending, to a greatest hits of ridiculous scenes that ends with Padme losing the will to live after she gave birth to twins? Are you kidding me, she gave up on Anakin and dies because of him turning, yet she says to Obiwan, "There is still good in him...."
Sorry George, I defended for 2 movies, but Episode III is a joke of a movie, and written so badly it just doesn't make sense. I feel my opinion is not biased like many because I actually defended George, but this movie ruined the trilogy for me, and it is sad, because it could have better.