Ikaruga has a wicked soundtrack. (Start at 3:04 if you want to skip the menu music).
So does Crimzon Clover.

Bastion is also worth mentioning.

Castlevania has good music throughout the series, with different versions of Vampire Killer and Bloody Tears as timeless classics

I'm also partial to Super Meat Boy

I'll recommend the Gyakuten Kenji 2 OST if anyone has played Capcom's Ace Attorney series, I just wish Capcom would port all their Jewels to steam like Danganronpa devs did ... ;_;

Some of my recent and all-time favorites:

• Metal Gear Rising: Revengeance
• Darksiders II
• Killer Instinct

These have been probably listed, and I don't know if its rude to post it without cheching allllll the posts

machinarium Be careful with "by the wall"
the tree of life easy to find songs, but not the full stuff
same with the master

https://www.youtube.com/watch?v=XVcUTAdHWtc Xenogears is probably my absolute favorite but really anything by Yasunori Mitsuda is great.

Omega Boost opening soundtrack (Japanese version).

If I remember right is Feeder - Shade

Obligatory:
https://www.youtube.com/watch?v=iW_Ct49H1ng

I'm just here to bookmark all this music :D

I'm really surprised nobody has said anything about Risk of Rain.
It has an absolutely awesome soundtrack.

https://www.youtube.com/watch?v=P5ChKb_9JoY

Enjoy.

for a more, somber, mood.
Silent Hill 2
Silent Hill 3

And for Gordon.
hellz yeah

Playing The Last Door and really enjoying the soundtrack.

And here's my playlist (that I just created (: )

Just scanned through the first page, didn't see anyone put Metal gear solid (plz don't kill me if it has already been done XD [I don't like the first few, due to their 8-bit annoyingness, but the latter are definatley worth listning to :D])

https://www.youtube.com/watch?v=0IMVwa6Km-I

This is also a really good one, probably my favorite in terms of Battlefield!

https://www.youtube.com/watch?v=SV0IF4XVBlE

I would say chrono trigger, but it's already take (seriousley though, get a snes emulator, and get the ROM for Chrono Trigger, and play it; Defenatley worth a couple hours of your life. By far, my most favorite RPG of all time.)

I'll post more as I think of them, but GREAT discussion topic! Can't wait to read through the list!

[Edit]

Just remembered; Dream! Nobody liked the game (besides me; I am an odd ball XD), but everyone LOVED the soundtrack! It's awesome!

https://www.youtube.com/watch?v=19XqlKxB3C0&list=PLhPp-QAUKF_iFtRR8rRWSQqqDBf6blV3i

And Ori and the Blind Forest! GREAT soundtrack! GREAT game! Definatley going to buy it once I have money XD

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

And here is the last one (Not that I could think of, but that I will post, due to me probably flooding the comment section with a huge list of soundtracks XD); Unravel. Gotta love the Scottish/Celtic feel!

https://www.youtube.com/watch?v=b5fun5L52Vk

And I can't believe I forgot this little all-time favorite series...
Die Waffen, Legt An!

Page 3 and Still no Life is Strange???

https://www.youtube.com/watch?v=Bh1Pr6ef_XI

No More Room in Hell Original Soundtrack Volume 1
https://www.youtube.com/watch?v=LKM6FA2x6_k

Don't Starve has some of the most beautiful OSTs ever. Let me know!

Don't Starve Soundtrack - Summer Jobs

Don't Starve Soundtrack - Summer Showdown

Don't Starve Soundtrack - For the Glory of Spring

Don't Starve Soundtrack - The E.F.S of Winter

Mirror's Edge and Mirror's Edge Catalyst's soundtracks have some incredible, atmospheric music. It can range from relaxing to very tense, but it's all really good. Assassin's Creed 2 and 3 have some great soundtracks. 2's is really atmospheric and made by the great Jesper Kyd, and 3's has a very cinematic and dramatic feel. I'd also recommend Hitman Blood Money's soundtrack.

Super Mario RPG

Trace Vector

http://store.steampowered.com/app/297410/

Symphonic Legends Nintendo themes played by a symphonic orchestra.

Edit:
Symphonic Shades Best of Chris Hülsbeck

X Rebirth

Novastorm