Although I like many things from many places, in video game music I find myself loving what the Japanese do more than anything.
I think Nintendo have made themselves a pretty kick ass collection of composers who understand game music to the finest level, and that must be thanks to Koji Kondo's taste, who most likely hired them. So here are the Nintendo guys I love:
Koji Kondo (obviously)
Hiro Tanaka
Taro Bando
Soyo Oka
Kazumi Totaka
Naoto Ishida
Yumiko KametaniThen of course,
Hitoshi Sakimoto who I think is probably the most clever arranger in game music,
Yasunori Mitsuda, who's been often copied.
Masaya Matsuura is pretty fucking out of this world too, the music from Vib Ribbon is a work of absolute genius.
For the non-japanese composers: I loved the music from God of War 1 and 2, and also what
Greg Edmonson did on the Uncharted games.
I also want to name of few Canadian composers who you have never heard about and who are to me absolutely unsung heroes: the in-house composers at Gameloft Montreal, you can trust me, I hired them back when I was head of audio there haha.

If I must name only a few, I'd say
Arnaud Galand,
Matthieu Vachon, and
Alexandre Jacob. Alex wrote the soundtrack to Gameloft's iPhone game "Castle of Magic", and I'm not kidding when I say this is some of the most fun, playful music I've ever heard in a game. The game itself is so-so, but god the music! Arnaud Galand wrote the superb soundtrack to the XBLA Prince of Persia Classic. He's a guy who was a pop/jazz pianist touring with bands all over Europe for 15 years, and got interested in game music by the beginning of the 2000's. You wouldn't think because of his background, but he really did his homework (I like to think that I helped a little:), and now you can hear him say things like
"the music from Chrono Cross is fucking awesome".
Jake "Virt" Kaufman was once part of the team, if that tells you anything about how good these guys are. Virt is also on my list of game composers extraordinaire, everyone was always impressed at the endless number of styles he could study and execute perfectly. Over the years, in-house composers at Gameloft have produced quite a few game soundtracks that I think are as great as they are unknown, and the company seems unable to understand that they could make an additional profit by selling those on the side.
Also, let us not forget that Michael Giacchino started as a game composer. Which I think is awesome. But I admit I've never played any Medal of Honor game, or any game scored by Giacchino.
EDIT: How could I forget Tomas Dvorak aka Floex ? The music from Machinarium is most refreshing thing I've heard in years, not only in game music. It's incredibly innovative, fun, and beautiful.