Best video game OSTs in my opinion are as follows (not all-inclusive):
- Xenoblade Chronicles (Wii)
- Trace Memory (DS)
- The Legend of Zelda: Majora's Mask (N64, 3DS)
- Silent Hill 2 (PS2, XBOX, PC)
- Silent Hill 3 (PS3, PC)
- Dark Cloud (PS2)
- Monkey Island 2: Anniversary Edition (PC, PS3, 360)
- thatgamecompany Games - flow, Flower, Journey (PS3)
- The Elder Scrolls IV: Oblivion (PC, 360, PS3)
- The Elder Scrolls V: Skyrim (PC, 360, PS3)
- Bioshock (PC, 360, PS3)
- Bioshock Infinite (PC, 360, PS3)
- Super Mario Galaxy (Wii)
- Fable: The Lost Chapers (XBOX)
- Final Fantasy III (DS)
- Assassin's Creed II (PC, PS3, 360)
- Mother/Earthbound Beginnings (NES)
- Kingdom Hearts Final Mix (PS2, PS3)
- To the Moon (PC)
- Stronghold (PC)
- Animal Crossing: New Leaf (3DS)
- Super Smash Bros. series but that's kinda cheating (N64, GCN, Wii, Wii U, 3DS)
- Pokemon HeartGold/SoulSilver Versions (DS)
- Pokemon Diamond/Pearl/Platinum Versions (DS)
- Pokemon Red/Green/Blue/Yellow (GBC) but that's mostly just nostalgia :)
...to name a few ;)