FF XIII has a very good soundtrack even if not as memorable as some other entries in the series: Among the best are:(The battle theme is obvious so I wont even bother)
Prelude - http://youtu.be/RIbo3Z7DmkQ
- I watched the opening atleast 1-2 everytime I booted up the game, it was glorious.
The Archylte Steppe - http://youtu.be/PBoBO0YMBys
- I spent atleast 15 hours running around this field, it was fantastic, easily the most fun part of the game. The soothing music totally nailed the right atmosphere. The first time I saw this area, I was blown away, It looked so good that I couldnt believe it. It's easily the best looking game of this gen imo.
Will to Fight - http://youtu.be/JN9ulQ2P9Qg
- The vocals during 2:50-3:50 really create this unique mood and are catchy as all hell. It's easily the best dungeon theme in the game.
Of the little that I played of XIII-2 I absolutely loved:
Invisible Invaders - http://www.youtube.com/watch?v=WUSHpQ2vuI4
- Skip the first weird minute, then it's awesome.