The one i keep on listening to is Sonic music ( most particular sonic 3 and knuckles, and both adventure games) Majority of the Street fighter games soundtrack. But castlevania symphony of the night has been taking up my time for some time now
The soundtrack for Xenoblade Chronicles is nothing short of amazing. I like how they chose more than one composer for it, because while I love Yoko Shimomura's score, I don' think she could pull off the right kind of sound for certain tracks, like this one [link].
The Metal Slug series has excellent soundtracks, mostly with nice blends of jazz rock, and other genres. Also, they have some awesome time signatures that really pick up the atmosphere I recommend music from any of the eight outings!
My vote is on Elder Scrolls V: Skyrim and Halo: Reach I pump the volume up and get goosebumps. Once a neighbor knocked on my door while I was listening to Halo Soundtrack and asked what is that awesome composer I'm constantly listening to
I'm a slave to NES Megaman music, but Megaman 2 has the best of the best.
I also love:
Double Dragon Neon The Terminator (SEGA CD) Earthworm Jim: Special Edition Street Fighter II TMNT: The Arcade Game Batman: The Video Game (NES) Journey To Silius Chrono Trigger All Dragon Quest tracks Sonic CD (Both U.S. and Japan versions)
My mind always falls back on good ol' EarthBound. It's got a quality to it that no other game has replicated, and it's something that I'll never get out of my head.
Other games that stand out are Nier (which had a very unique take on lyrical and vocal performances), the Jet Set Radioes (Like the best Urban, techno and hip hop mixtape I've ever heard) and Moon: Remix RPG Adventure (Like the best new age and experimental music mixtape I've ever heard).
-Brawl (the diversity of genres makes it interesting) -World of goo (Quite some environmental music) -Silent hill 2 (I like how it has both creepy and emotional tunes ) -Mario strikers charged (Nothing you would expect from a normal Mario game)