Adding my voice in for Xenoblade Chronicles. I dragged out the final boss battle just so I could listen to The God Slaying Sword, and I somehow never got bored of One Who Gets In Our Way, despite the fact it was used for pretty much every boss battle. Then there were the field themes...only Hills of Radiant Wind from NieR can compete against Gaur Plains, in my opinion.

Baten Kaitos had some pretty good music, too; easily amongst Sakuraba's best. The True Mirror was my favourite battle theme for ages.

The Atelier series boasts some fantastic tracks, too...especially the Arland trilogy. It's all so delightfully whimsical! Cadena is one of my favourite opening songs for how wonderfully bubbly it is, and whilst a lot of the music is just a variation of a single track, I like how it all builds up. Totori changed the tone of Following the Footsteps depending on your location, and Meruru's overworld music changed depending on how developed your kingdom was. I like stuff like that. Plus there was Hagel's theme...

Ar Tonelico gets a special mention for its vocal tracks, which easily rival NieR's. Not only is Akiko Shikata a fantastic vocalist, but the fact that the songs fit into the game's mythology give them a greater significance than the norm and just make me appreciate them more for it.

The Legend of Zelda: A Link Between Worlds had a spectacular soundtrack, as well. Zelda OST is generally pretty good by-and-large, but ALBW was just one giant fanservice album. So many classic tracks remixed to perfection! I also really liked Mother Maimai's theme for some reason. Lorule Castle had a nice build-up as well; the more you did, the more epic it got, until it goes full blast with the vocals at the end. Yuga having a vocal battle theme was nice too.

...I'll edit this with more and some samples somewhen. I listen almost exclusively to game music these days, I have a LOT of favourites. xD