Saying that the Hades OST is my favorite soundtrack seems like the obvious choice out of Darren Korb's immaculate work on Supergiant's games is the safe pick. I'm still going to say it's my pick though.
Honorable mentions include Fastfall from Dust Force and the Metal Gear Rising Revengancs OST
Venus lighthouse from golden sun. It's still my ringtone!
Descent II OST
Cyberpunk 2077 has pretty damn good music with a large variety of styles. I love that they have almost exclusively artists Ive never heard of and whose great music Ive discovered that way.
Ultima VIII also had really good music, so perfectly eerie for this bromen world. From the same artist also Wing Commander: Privateer.
Tyrian had a great soundtrack that sounded really oldschool 8 bitty and perfectly supported, nay made the athmosphere of the game.
Dune though, that has to be one if the best. What that artist produced using just the measley OPL3 FM synthesizers of the first soundcards? Absolutely incredible.
CP2077 has the best character creator music I've heard by a mile. Great for someone like me that spends over an hour in that sort of thing.
Dune was outstanding. If you haven't heard "Arrakis (Wormsign Remix)" from OCRemix, check it out.
Ocarina Of Time and Super Mario 64 for sure.
Megaman and Donkey Kong Country also have some great chiptune music.
And The Witcher 3 for including so many different traditional instruments. The Elder Scrolls is also good.
Donkey Kong Country
Aquatic Ambiance has never not been on my cell phone(s)/mp3 player(s) over the last 20+ years and that's how I likes it.
Ace Combat 7 - https://www.youtube.com/watch?v=-kVdCaczLE8
Project Wingman - https://www.youtube.com/watch?v=xgcap-5IBsY
Pathfinder Wrath of the Righteous - Almost all of their mythic path themes and then some. https://www.youtube.com/watch?v=vCpTyQU3Vt4&list=PL5LsN8A6ix5qmFLYtrjWxP7zZOoffuuDr&index=8
And of course people here mentioned a few good ones like Undertale, Stellaris and stuff like that.
The classic! For me, I gotta give it to Heavens Divide from Peace Walker. Such good music to pick from across the series.
Ori and the Blind Forest
The Marble Gallery theme from SotN is aboslutely burned into my mind still.
Hard to pick just a few tracks, but some of my favorite original soundtracks are:
Nier Gestalt
Persona 5
The Witcher 3
Stellaris
For licensed ones, I particularly like Grand Theft Auto: Vice City and Life is Strange: Before the Storm.
Subwoofer Lulldlaby from Minecraft, Basically all of the Alpha album Minecraft music
The Furi OST is banger after banger. It's a who's who of syntheave artists. It's my go-to listen when I'm caffeinated and need to be productive.
Riding the Solar Wind - Stellaris.
Umm...let's try going through the ages
I was like 4: Gizmos & Gadgets ending theme. I'm pretty sure it's one of the few original songs The Learning Company did, there's very few clips of it because it was before even .wav was commonly used for music (due to file-size issues), it's a really cheerful song
Early Childhood: Space Quest 6 Main Theme is a bop, also Human 3 from the base game of Warcraft 2, and Orc 6 from the expansion. I miss the less ambient and more intense Warcraft music.
Listened to a lot of anime music around wc3's time...but peak music at the time was Sonic Adventure and Sonic Adventure 2, plus Phantasy Star Online thanks to the dreamcast. Especially 'Pray For IDOLA The Holy'. Grandia II also giving the Ver.3 and Ver.4 boss fights.
Nowadays with great music being everywhere? Probably Persona 5 in general.
The only game soundtrack I ever recall make a point of listening to is from Faster Than Light, it's some really good ambient music.
Oh, man. So many good ones, especially in the indie space. Celeste and Eastward both have spectacular, eerie, synthy soundtracks that are wonderful. Another indie game, Flinthook, has a theme song that absolutely slaps. Katana Zero had a rad OST, too.
Undertale goes without saying.
Obv Nintendo games, especially ones composed by Koji Kondo, have amazing soundtracks. OoT is one of my favorites, but there are many good ones. Basically any classic Zelda, Mario, Donkey Kong, etc. Even the newer games, like Mario Odyssey and TotK, have great soundtracks. While not first-party Nintendo, the first couple gens of the Pokémon games' music will live in my brain forever more.
I'm also gonna shout-out Grant Kirkhope because he is a genius and basically composed the soundtrack to my childhood. You know him from Banjo-Kazooie, Donkey Kong 64, Mario + Rabbids, and many more games. They aren't soundtracks I'd walk around listening to on Spotify (probably), but in the context of the game world, they are perfection.
I could go on, but I'm just gonna shout out my faves and walk away before this becomes a giant wall of text.
EDIT: Oh lord, how did I forget Halo 2's theme (Mjolnir mix)?
I regularly listen to the Subnautica OST while working.
Favorite instrumental soundtrack themes are from the early Silent Hill games. The theme from SH1 and the Theme of Laura from SH2 are classics.
Favorite lyrical songs used within the game for plot: Alan Wake has characters in it who are 70s rock gods called Old Gods of Asgard, and the creators got a group named Poets of the Fall to actually write the two songs that were featured from the game and they are actually really great songs. Poet and the Muse is a plot point and Children of the Elder God is played during a really good sequence.
Darksiders II has a phenomenal OST. I still listen to that regularly.
That being said the Burnout 3 music was great but obviously not an OST
I have five fingers on one hand so here are five favorites:
Maximum Anarchy's soundtrack
The Messenger has amazing music harkening back to the 8 and 16bit stuff from the MegaMan games. Underrated game in general too.
I love the Final Fantasy theme, in all its incarnations. But given how much I've played X4 Foundations, the original main menu music has really taken hold in my brain. And more recently, the Kingdom End DLC main menu theme.
Super Mario Galaxy
The Outer Wilds soundtrack is something I go back to regularly. Even considered buying the Vinyl...and I have no way of playing it.
The Chrono Cross soundtrack is just beautiful. I particularly like the opening song "Scars left by time"
This will be unconventional, but I loved the music from Darksiders Genesis by Gareth Coker, the same composer who did Ori.
Best 3 tracks in my opinion are tracks The Beacons, Astarte's theme, and the Credits/trailer theme.
My favorite game music comes from A Dance of Fire and Ice, although it may seem obvious that a rhythm game would have to have good music. Divine Intervention is one of the highlights for me.
Kk Slider slaps
Tbh any remix track from rythm heaven. Yesterday Rythm Heaven Reanimated (a fanimation) popped up on my yt feed and I cried listening to (I'm also unclear as to why. Some music just does that to me when I really like it)