Here's my take on the prequels.
(TLDR: Each one gets better, but they're ultimately a disappointment, and don't "line up" well with the OT.)
Episode I - When this came out, I saw it about 6 times. I was too caught up in the hype and anticipation to let myself notice the flaws. At the time, the coolness of the final lightsaber battle was enough to carry the film. But after a few months, I started to get this "What just happened?" feeling. Over the next few years, the flaws (mostly badly placed humor and a sterile story) slowly became too obvious. Now, I'll be perfectly happy if I never see this movie again. I'm not even sure Adywan can save it.
Episode II - I saw this 2 or 3 times. This was a much more mature film, and it seemed to be leading somewhere very interesting. In the hands of a different director (like Kersh), this movie would have been pretty damn good. The aspects of where the clones came from, as well as who ordered them, were very strong. But the romance was botched horribly, and Yoda's fighting skills were laughable. Still, I was a little more hopeful for Episode III after this. I was looking forward to learning who Sifo Dyas was.
Episode III - I saw this twice. At last, Lucas started to realize that these movies had to connect to the OT, so he tried to squeeze all of his buildup into this film. ROTS moves along fairly well, and it has some real emotion to it, unlike the first two. But the reasons for Anakin's turn are murky and undefined, and it seems to suddenly come out of nowhere. The major question set up by Episode II - Who is Sifo Dyas? - is never addressed. (Don't talk to me about a book.) It was with this episode that I realized the prequels had ultimately been a failure - the characters never grew in interesting ways, the humor was juvenile, and Anakin's turn (the reason we stuck with the prequels in the first place) was mishandled.