I love both the MT-32 and CMS versions of Ultima VI’s soundtrack, particularly Todd Porter’s contributions.
You can hear them all at the Video Game Music Preservation Foundation
When all the rumors of a Silent Hill remake were swirling last summer, I dove into listening to the first 4 games’ soundtracks. They really have such an ethereal quality that is hard to match. I particularly love Silent Hill 2’s atmosphere just based on the music alone. There were a few days were our city was blanketed with smoke from wildfires, and boy did those tracks feel a bit more real as I walked through the deserted parks.
Another series with great music is Ace Combat. The soundtrack for 7 was on a weekly rotation for awhile after I finished he campaign. I’ve only really listened to the OST for AC4 and AC: Zero, but I’ve heard there is a lot of love for the other games as well.
The NES first two Ninja Gaiden games. Everyone focuses on the difficulty, but the soundtracks were pretty great. The original is the first game I remember that had drums that actually kinda sounded like drums. Also the opening scenes were awesome musically and cinematically, at least to 8 year old me.
Mega Man 2 has always been a favorite of mine as well as Final Fantasy 6.