I was thinking today..and I might know why the music in WW sucked.
NOTE: THIS IS THEORETICAL, AND MAY SOUND ********
The Gamecube music in AC sounded amazing, and was probably due to the fact that Nintendo was able to fit better music of bigger file sizes on discs. Though, looking at how the DS is a miniature N64, the music was a little crappier to be made to fit on a DS cart. Hence they also had to make room for the graphics, textures, etc., while AC for Gamebcube maybe could have fit it in with good graphics to the the well known fact that: Discs can fit more than cartridges. Discs = 8-9 GiB., DS Carts = 3-4 GiB. (or so i've read), meaning the music had to be small and of low quality. The music in GC probably sounded better because it used more notes and composition. The DS on the other hand, could only fit so much. Which is why looking at the Wii's capacity, I believe there will be new music, and only time will tell if that music is good or not. Me, being an AC veteran, can't stop myself from buying this. Why? Because I'm a total addict. But that's beside the point.
Again, this is really theoretical.