Personally, I find the music to be just about the only enjoyable element of the PT. The movies suck, granted, but I still say Williams delivered solid scores for all three films (AOTC is admittedly the weakest of the lot).
As for your comment that "none of the music within them [the prequels] has ever stirred any sort of lasting impression in me," I can sympathize. But I tend to think that that's a result of the lack of decent storytelling and characterization in the prequels. The OT scores are more emotionally meaningful to you and me because they play upon a "connection" of sorts that we've formed with these characters whom we have come to know and love, and with the gripping storylines as well. When it come to the PT there's no such connection to play upon, because the source material was too shallow to begin with.
That being said, I think the PT scores qua scores are just fine.