I’d have to go with Flatout 2. Incredible game, incredible rock and metal tracks.
Dont think I have a single favourite there are too many greats to love:
Goldeneye 64 original from the days of Rare’s greatness, theres also a great remake soundtrack on youtube.
Hollow Knight, Christopher Larkin just nails it (the track “Lace” for the upcoming sequel slaps too)
Celeste, just amazing work by Lena Raine
Katana Zero, my current go to “work” music.
C&C 1 Not all great but there are a lot of good tracks on that soundtrack, and it opened my eyes to game music.
C&C Red Alert 2, Hell March 2 is just awesome, the rest of the soundtracks slaps.