The Phantom Menace is, by far, the Prequel film I enjoy the most. Revenge of the Sith is, without question, the least entertaining of the six Star Wars films.
The problem is that if Lucas really wanted to do the Prequels, he needed to do them backwards. Doing them in chronological order was a bad move. The reason Phantom Menace works is that, in 1999, we had no real idea how the Star Wars saga began. We knew things that had to happen before A New Hope, but otherwise it was a blank slate. And Phantom Menace had that blank canvas to work with. It could do new and original things.
Unfortunately, by marking out where the saga began, you can draw a line between Phantom Menace and A New Hope. You begin to see that Anakin will have to impregnate a woman to bear his children, you see that Anakin will have to fall, you see that Palpatine will have to usurp power. Combined with what we thought we knew, plus the starting point that Phantom Menace gave us, the broad outlines of a galactic crisis were drawn, and once we reached Revenge of the Sith, that movie did absolutely nothing unexpected.