The Phantom Menace was breathtaking in 1999. The production values, visual and sound effects were flawless, but Jake Lloyd was annoying as hell. As for Jar Jar, I don't see what the problem was outside of him being the second most annoying character in the movie (someone had to fill in for C-3PO's lack of screen time). But why was the character such a racist stereotype? He was voiced and mocapped by a black guy imitating his grandmother!!!
For the boring first half, Attack of the Clones transformed into a work of genius during the last hour. (And even in the first half, there's an unintentionally funny love story that in and of itself is a genius in its stupidity.) Say what you want about George Lucas's inability to write character dialogue, but the guy can sure design and create some of the most memorable action sequences on either film or digital video.
I had no major complaints about Revenge of the Sith, outside of Hayden Christensen's tired performance, and the false pretense of this being the darkest of all of the movies. Just because it's the only movie of the six to get a PG-13 rating doesn't mean it's the darkest, George. The Empire Strikes Back was darker, I think. But depending on my mood, Sith is either my second or third favorite film of the entire saga.
And none of the prequels are my least favorites of the saga -- that honor goes to Return of the Jedi. God damn Ewoks.