In-Game Music

[CountArach]

Tetris is the pinacle of game music.

[Crandaeolon]

Seconding Monkey Island (Michael Land), great uplifting tunes there.

Also seconding Star Control 2, it was one of the first PC games to utilize tracker (=sequenced samples) music - Riku Nuottajärvi did some great pieces for that game, including the hyperspace music.

From the Amiga era, Turrican 2 (Chris Hülsbeck) comes to mind. Still often remixed. Stephane Picq deserves a mention for the original Dune soundtrack as well - perfect fit for the setting. Shadow of the Beast (David Whittaker), particularly the second one, was good for the ears too.

Commodore 64 had some great music despite its limited resources. Ocean Loader (Martin Galway) anyone?

In the modern PC era we have Jeremy Soule (Total Annihilation, Morrowind, Oblivion, Icewind Dale etc...) but he's IMO a tad overrated musically (his technical achievements deserve high praise though) - many of his games have good theme musics, but the rest is pretty "stock" material. Some exceptions that come into mind are the previously mentioned TA soundtrack plus the soundtrack for Guild Wars: Eye of the North, which has surprisingly many good pieces of music.

Mark Morgan did fantastically fitting music for Fallouts 1 and 2 and Planescape: Torment. Inon Zur has some big shoes to fill for Fallout 3, so far most of his music (that I can remember) has been nice but far too cheerful.

I'm not all that familiar with consoles, but something that wasn't mentioned yet is Actraiser - absolutely great soundtrack, especially in symphonic rendition. Mega Man 2 left an impression too.

[Pannonian]

Tetris is the pinacle of game music.

I beg to differ. There isn't any videogame music that's as annoyingly persistent as this.

Bubble Bobble.