most memorable soundtrack you ever heard in a game

Metal Gear Solid, OST from the whole franchise is gold.

i can only remember of Life is Strange because just played it xD
here's the playlist (so awesome of the devs giving this for free <3)

Spacechem, surprisingly.

Almost anything done by Jeremy Soule, Inon Zur, Michael Hoening (Baldur's Gate), and Andreas Waldentoft.

天之痕。

deus ex: human revolution
https://www.youtube.com/watch?v=BvRbh1_vPCs

probably Epilogue of Hans Zimmer.

https://www.youtube.com/watch?v=Iy4iQvJo24U

All of Kameo

For me:

One of the Final Fantasy's (7 or 10 instantly come to mind);

Silent Hill 2;

Hotline Miami;

FTL;

Devil May Cry the first one (whatever m8 its imo so u wanna fite?)

To the Moon
Metal Gear Rising

Full of nostalgia:
Terranigma

Honorable mentions are Bravely Default, Xenoblade Chronicles and Ni No Kuni.
Of course there are more games, like Zelda, FF and many more which guarantee goosebumps :3

Surprisingly, there aren't many PC games, although some have really scores, like Payday and TES games, or the Civ4 main menu theme

Portal 2 :D

Bastion and Transistor. Darren Korb FTW!

EDIT: From games not mentioned yet, I also really like soundtracks for Frozen Synapse and Cave Story.

Need for Speed III

Black Moon Chronicles - https://www.youtube.com/watch?v=PypvWY2f3_c&list=PLF120EBCE7906D837&index=2

My favourite is the soundtrack of Alone in the Dark by Olivier Deriviere, the first track: https://www.youtube.com/watch?v=g3Ur3FWk7wg

Anything from Final Fantasy 6

The theme that plays frequently throughout Dungeon Siege I -- especially in the beginning.

Of course Jeremy Soule is fairly well regarded for many of his works.

She talks too much, but oh well: https://www.youtube.com/watch?v=zWpLH3Jxxl8#t=477

Mechwarrior 2 Soundtrack by Jeehun Hwang.

1) Tetris theme - I'm sure most of you would recognize the meldody

2) Super Mario Bros theme

3) Zelda theme

My most memorable has to be Majora's Mask.

Hard to forget Return to Kharak....

In terms of entire soundtracks, however, the old Black Isle games have refused to leave my skull since they first came out.

Baldur's Gate
Baldur's Gate II
Planescape Torment
Icewind Dale

(Honorable Mention: Diablo and Diablo Il.)

Katamari Damacy.

OK Mr Sunshine!

(Spelunker and Pitfall II C64 music still pops in my head every now and then too, good times......Bah! I'm old.)