This is a good topic. Thought-provoking.
As an unabashed prequel hater, I also realize that everything exists on a continuum; nothing can be absolutely "bad" or "good." Even though I generally think that the prequels are vastly inferior to the classic trilogy, I do like certain moments in the prequels:
1) The action set-pieces in TPM. The pod-race and "Duel of the Fates," if not necessarily rising to the level of the classic trilogy, got the juices flowing and people talking. Which is really one of the main functions of cinema in the first place, in my opinion.
2) Liam Neeson. He carries TPM. No other actor carries the other two prequel films. That's one of the many reasons why they're both such a terrible, out-of-control mess.
3) A certain walking and talking scene in Episode III. Obi-Wan: "Yes, but use your feelings Anakin, something is out of place;" and "The Council is asking you." Just a good, well acted scene by Ewan all around. If most of the prequels' scenes were this good, we wouldn't be having this conversation.