Super Mario Galaxy. In fact, it might have the best soundtrack of any game I've ever played. It has the vibrant energy the series is known for, but also some more atmospheric, epic, and melancholy pieces that truly stir the emotions.
The Observatory
https://www.youtube.com/watch?v=5sN2DpfOhTo
Dino Piranha
https://www.youtube.com/watch?v=Yqyterw15c4
Gusty Garden Galaxy
https://www.youtube.com/watch?v=IVH6Gl7W0hI
Melty Molten Galaxy
https://www.youtube.com/watch?v=F6i96e3fSdk
Galaxy Reactor
https://www.youtube.com/watch?v=Y_n3dKdDxsQ
Final Battle
https://www.youtube.com/watch?v=6zBVkp-aR_M
Family
https://www.youtube.com/watch?v=wTrXEobdx2I