An old example has to be Soukaigi on PlayStation. Really not a great game but I thought it sounded quite unique. It was composed by the same guy behind Secret of Mana's beautiful soundtrack but with an actual band this time. Has that 90s game sound, though, which I secretly love.
https://www.youtube.com/watch?v=WO7nSb9evnQ&index=3&list=PL74A294E9C891A8C2
https://www.youtube.com/watch?v=JqDjbQInDPA&index=14&list=PL74A294E9C891A8C2
https://www.youtube.com/watch?v=E5tQZtN7eSk&list=PL74A294E9C891A8C2&index=12
		 
		
	 
Good call, I remember when I first heard this soundtrack I was blown away. Still haven't played the game cuz I heard it was crap. But man that OST is amazing.
	
		
	
	
Took way too long for this to get mentioned, but it seems to be getting the love it deserves now.
Anyhow, some more additions:
Metal Gear Solid: Peace Walker: has a great soundtrack, especially since it was the first mainline Metal Gear without Harry Gregson Williams since MGS1. Such a great OST, they still used parts of it in Phantom Pain. For a portable entry to the series that most people skipped, it's friggen amazing. Not to mention one of the best boss fight songs of all time.
Peace Walker Main Theme
Snake finds Chico
Love Deterrence
Drakengard 3: great OST, low budget and average gameplay. Hell even if the only amazing track on the OST was This Silence is Mine, the game would STILL have over delivered based on that track alone. So good.
Decendeus
The Black Song
This Silence is Mine
Lunar 2 fits too, because while I thought the original Sega CD Lunar had a great OST, Lunar 2 just completely destroyed it. It's a shame that most people know the PSX version of these tunes more than the Sega CD ones, because the original instrumentation was just better in every way. Noriyuki Iwadare is one of the unsung great in the industry, and Lunar 2 is probably his masterpiece.
Field to Tomorrow
Footsteps of the Decisive Battle
Lucia's Decent - Sorrowful Memories
And finally 
Tenchu. Tenchu was a great game, but holy crap it's soundtrack blew me away, the OST was done by Noriyuki Asakura of Rurouni Kenshin fame, and it worked, and worked well. Hell, I was barely able to play much Tenchu 2 because it didn't have music in the levels, it drove me nuts. I could post the entire soundtrack and feel good about it.
Battle with a Fierce Enemy
Cross the Checkpoint
Execute the Corrupt Minister
So there we go, I'm sure that someone will also eventually bring up 
Shenmue 2, but here's a song that over delivered in a soundtrack that over delivered.
Waves in the Morning Haze