my personal list
touhou hrtp- eternal shrine maiden. im not too fond of the pc98 games, but zun definitly had his magic touch back then as there are still some excellent tracks in these
touhou soew- complete darkness. i dont know of many tracks specifically from this game (asides from theme of eastern story) but mimas theme in this feels intense, and very well made. honorable mention is love colored magic
touhou podd- reincarnation. speaking of mimas theme, another classic pc98 track. im not too familiar with podd ost, but reincarnation is probably the pc98 track i come back to the most.
touhou lls- sleeping terror. honestly a really hard pick, this one has a lot of really good tracks, but i decided on sleeping terror. its the track i think of first when i think of yuuka, and this game as well. feels like a final boss them despite not, zun probably made both this and inanimate dream and wanted to use both.
touhou ms- legendary illusion~infinite being. man, who couldve seen this coming lol. another hard pick, as this ost also has a lot of really good tracks, but i have a bit of a bias towards this one. it was one of the track that introduced me to touhou, and is one of the only other pc98 tracks i keep going back to. it feels almost like some of the later final boss themes in the series, going for a more cinematic and climactic approaches. honorable mention to romantic children.
i will come back tomorrow and tackle the next few games.