Tough one.
Great tier
Id say Nemesis, Wicker Man and Th13teen all have pretty good soundtracks which help build the atmosphere. All 3 fit the theme really well. And I do always enjoy it when they take 'in the hall of the mountain king' and work it into the ride music.
Okay Tier
Galactica - Space soundtrack seems a little bit cheesy and generic. But at least it does fit the futuristic feel of the ride. Personally liked Air slightly better.
Bad Tier
The Smiler.
Yes, I know this is going to be a controversial one but it's just my opinion.
The smiler theme is a big offput for me whenever I walk past it. I find the noisy laughing played on the speakers really annoying and repetative. Im just not into the whole laughing gas/ brainwashing theme myself but I understand why others might like it, it certainly fits the crazy layout of the ride.
Oblivion Tier
Step back into the 1990s with this really outdated theme. The music doesn't really reflect the ride. It should be more dark and mysterious. Currently it gives the ride very little atmosphere.