I noticed it with TPM and it's something that stuck with me through the other two prequel soundtracks- the music was banal. There were excellent themes from all three, though, obviously the Love Theme from AOTC, Duel of the Fates, and Battles of the Heroes. I suppose that it's a sign of the prequels being different in tone than the OT, plus John Williams being older and maybe having some different musical influences and techniques than he did for the OT.