It goes without saying that I like Touhou music (mostly electronic arranges of the original themes, that's what I'm listening to right at this moment), but special mention goes out to games that have music like from Final Fantasy - Crystal Chronicles. And sometimes when the latest hip hop comes on the radio, before I change the station to something else I notice that the simple, catchy background tune behind their 'singing' sounds a lot like Metroid Prime music. I like Metroid Prime music.
And since it's more recent, I must say that I really like Starbound's main menu theme, and most of the peaceful planetary exploration music. I just wish it didn't get interrupted every 15 seconds by combat music caused by KILLER SPACE BATS WITH LASER BREATH.
Let's see, what other games had really good music... Xenosaga is nice. Oh, must not forget Chrono Trigger. Between Time Circuits and the themes for Schala and Belthasar, not to mention that epic Lavos theme...