My favorite video game track of all time is Sky Sanctuary Zone from Sonic & Knuckles.
http://youtube.com/watch?v=oNXBpzDp1K8
However... there is one song that may steal my heart. The more I listen to it, the more amazing it becomes... Gusty Garden Galaxy from Super Mario Galaxy
http://youtube.com/watch?v=A0R6FnpqylE
Other Notables...
Metropolis Zone (Sonic 2)
http://youtube.com/watch?v=yRuJfhEeCe8
Rattle Battle (DKC2)
http://youtube.com/watch?v=vT9w3zk5vsc
Skytown (Metroid Prime 3)
http://youtube.com/watch?v=7P7jdnU06ew
Opening (The Legend of Zelda: Wind Waker)
http://youtube.com/watch?v=zJCsOte2bcw
Metal Gear Solid 4 Love Theme (SSBB)
http://youtube.com/watch?v=uUfKFElJ9sA