This I agree with, ZUN's old works are much more expressive. Even in the PC98 days, he had a tendency to go crazy with the number of voices, many of which are redundant, but it was kept in check by hardware limitations. He seems to be getting better though, games 13 and 14 have many tracks with great melodies reminiscent of his older stuff.
I also find that the PC98 game soundtracks are consistently great while the Windows games have one or two standout tracks per game and the rest are forgettable. Overall, Mystic Square is my favorite.