Ooh...I have an entire playlist of my favorite OSTs. Long term, I'd have to say One-Winged Angel, specifically the remake. Also worth mentioning:

Dark Soul 3 main theme

Feel from Lies of P

Dependent Weakling from Nier, specifically this version: https://www.youtube.com/watch?v=ePXlfGufSjk&t=0

Mass Effect 3 - Leaving Earth

Scored by the great Clint Mansell, also check out The Fountain OST.

I think this might be at a sweet spot between being a well-known track and an unexpected top choice to answer this question - Kefka's theme is iconic.

I'd still put FF6 as my top game soundtrack, but I'll admit it's easily possible that's just a consequence of me not playing many games the past couple decades.

Jazz Jackrabbit 2 OST Carrotus

Dearly Beloved

The track during the balcony scene from the first Blade Runner point-n-click adventure game. Came out in 1997. It's Vangelis' iconic Blade Runner Blues

NieR: Automata - Weight of the World

This is at first so beautiful, and later on it just hits so hart. And listening to the other versions, japanese where the performer even cries, and chaos (a fantasy language) (video with spoilers, sadly), this is such a great piece of art. The perfect bittersweet song.

Just one?

Portal - Self Esteem Fund by Kelly Bailey

The volumes this song speaks through it's atmosphere is incredible. The raw emotions and feelings of isolation are better conveyed through this song than words ever can in my opinion

My scrobbles say I've listened to this single song for more than 9 hours over the years... I have so many emotions bottled up in this song lol

Red Alert Hell March

https://youtu.be/e3YzmjmAGoI

To Zanarkand just does something...

The perfect synchronicity of the Metal song and the player character pumping their shotgun at the end of the opening sequence of DOOM (2016) when they exit the elevator towards the surface of Mars.

Justin E Bell - All Gods from pillars of eternity

https://youtu.be/2bqVB1MCN2c

Metal gear solid- the best is yet to come

Probably nostalgia but guild wars 1 specially prophecies ( the first / base game ) had some absolute bangers for an mmorp and specially fitted for zones.

https://youtu.be/Xi3uIEEhxo8

Expedition Society theme from Pokemon Super Mystery Dungeon. Has some commie marching song vibes.

Vigil from Mass Effect. I think it's the song playing when you first get the galaxy map, and playing that game and seeing the world open up while hearing that song really put me in a great mood.

Aquatic ambience - donkey kong country

I'm partial to the original Dwarf Fortress music

Rusted apart from the unravel. That music is just too good

Hard to pick just 1, so here's a list of ones I deem notable from a few different games:

• 14.3 Billion Years — Outer Wilds
• Undertale — Undertale
• City of Tears — Hollow Knight
  • (with in-game ambiance)
• Under the Eye of Kibenya — Heaven's Vault
  • No publicly available version of this one; but the game and soundtrack are good, so they're worth a buy
• Private Room — Five Nights at Freddy's: Sister Location
• Tiny's Theme — Mario Golf
• Cleopactra — Ms. Pac-Man Maze Madness
• Dive Into the Mellow — Sonic Adventure 2
• Fathomless Tomb — Deep Rock Galactic
• They Might As Well Be Dead — Risk of Rain 2
• xX_TF_CNS_FloatingBits_Mp3_Xx (Floating Bits) — The Finals

There are a lot of good songs, but today I will pick Megalovania by Toby Fox. https://youtu.be/KK3KXAECte4

Laura Shigihara - Everything's Alright from To The Moon.

That game made me weep like a baby, so even now, some ten years after playing it for the first time, that song still stirs up those feelings.

And for much the same reason, Daniel Lanois - That's The Way It Is from Red Dead 2.

If you've played it long enough to hear that song, you understand.

Gotta say, nobody knows this game and rare are thoses who even played it, can it even be considered as a video game track, but i will say the first theme from Irisu Syndrome!

Original music: probably everything Solar Fields did for Mirror's Edge. Not original: No Rest for the Wicked is perfect for Borderlands. Hard choices though, there's a lot of good shit out there.

It has to one of these two for me, hard to pick: The Chersonese soundtrack from Outward or Fear Not This Night from Guild Wars 2.

The Outward one hits especially hard while adventuring through Chersonese!

Edit: typo

My mind landed on Stickerbush Symphony from Donkey Kong Country 2 and kinda settled there. David Wise is damn good at composing video game music.

Tristram from Diablo

Guile's theme from Street Fighter 2

they still play in my head regularly, 30 or so years later

Cassette Beasts OST is amazing. "Wherever we are now" is probably my favorite.

To me it's always been the B version of the original Tetris. This and most of Megaman X

Mick Gordon and Tex Perkins track from Wolfenstein: The Old Blood, called The Partisan. Fantastic end piece to the game.

https://mickgordon.bandcamp.com/album/the-partisan-feat-tex-perkins

Later found out it's steeped in history as it's a cover/adaptation of a 1943 anti-fascist song written in French by Russian-born Anna Marly. https://en.wikipedia.org/wiki/Anna_Marly

Chemical Plant Zone, Sonic 2.

This is gonna be an old cut but Paperboy the arcade by Atari frickin slaps.

Max Payne 2: ”Late Goodbye” by Poets of the Fall.

Metroid Prime OST, too many good options to pick just one.

I have a new obsession: Sea of Stars

https://youtu.be/Xer_vasWKGQ

https://youtu.be/GYLdQZQ0YT8 Distant Worlds II: The Prelude, if that counts as a video game track.

https://youtu.be/STPnXPSirT0 With this as continuation.

https://youtu.be/lndBgOrTWxo Otherwise Stickerbush Symphony.