All of them are pretty great, though a few stick out:
1. MA has the highest average track quality, and the Necrofantasia arrange tops it off perfectly
2. CoSD is a close second
3. DiPP, while not strictly a Touhou CD at first until it got retconned, gives off vibes of a primordial and dark Gensokyo which I like very much
4. TJD blew my expectations out of the water, to be honest. DBOA and DLFR were just average for me, so by comparison this album knocked it out of the park. There's classic style fantastical Touhou in Taboo Marionette, there's Debussy-style impressionism in the first track, there's "wheee LFG!!!" in the Necro-fantasy arrange and in the last track. Really satisfied with this one.