(BGM = background music)
Don't play many video games.
Technically, this was used as background music (it plays once every 5 or 10 minutes when you're wandering around):
Oh Golden Sun, you can truly do no wrong. <3
Outside of Dark Dawn, that is.
Lower Norfair/Magmoor Caverns (Metroid)
Hyrule Field (Twilight Princess)
Definitely Halo Reach's. For some reason to me, it sounds better.
Kingdom Hearts, really any of them. But I'm partial to KH2's Reviving Hollow Bastion
Another big one for me. Shovel Knight's just great.
I really can't pick a favorite, considering all of the Zelda and Elder Scrolls games, but this is definitely one of my favorites: https://soundcloud.com/micah-henman/metroid-prime-3-corruption-2
I've gotta go with Skyrim for this one, but I also love the music for Minecraft and WoW.
Some of my favorites include the Hoenn pokemon themes, most kirby themes, halo themes, and Luigis mansion. There's a LOT more though.
Good ol' WoW, has always had great music.