Lateralus by Tool. This isn't literally the best album that I've ever heard, but it's certainly my favorite, and it's the only album that I can think of wherein I actually like every single song on it. Reflection, in particular, has been my favorite song for years now -- I've listened to it countless times, and could listen to it anytime and still remain enthralled by it.
In fact, thinking about it just made me listen to the song again. This is all your thread's fault.
And I can't help but smile when I listen to some of Weird Al's older songs.
But if I had to pick, I'd probably go with Asia. They've been around since the late 70's, and still come out with new stuff. While the band has changed considerably throughout the years, I'm still amazed at how well put together they are.
I just successfully tested changing music by region, and changing it between continents on the world map after getting on/off the airship. I had to override the default audio transitions with eventing to make it change smoothly but it worked.