Jeremy Soule is probably the number 1 VGM composer, at least in the west. He's done more games than I can count, from his incredible soundtrack for Total Annihilation and Supreme Commander to the scores for Morrowind and Oblivion. Look him up for 5 minutes if you do nothing else today.
Some of my other favorites include:
Alexander Brandon - Jazz Jack Rabbit 2, Unreal Tournament, Tyrian
David Wise - Donkey Kong Country/Diddy Kong Racing (all of them), Battletoads
Tommy Tallarico - Earthworm Jim, MDK, Wild 9, Prince of Persia + countless others
Frank Klepacki - Every C&C game except Generals and 4, Universe at War
Bobby Prince/Lee Jackson - Duke Nukem 3D, Rise of the Triad, Major Stryker
Bill Brown - C&C Generals, Rainbow 6 series, Lineage II
Matt Uelmen & Glenn Stafford - Lots and lots of Blizzard's music for all games
Mark Klem - Wacky Wheels (but Wacky Wheels had such a good soundtrack so it gets listed!)
And if you're looking for a more eastern feel, check out Isao Abe, Taro Bando, especially Nobue Uematsu, and most definitely Junichi Masuda. Those last 2 are responsible for pretty much all Final Fantasy and Pokemon music, respectively.
OH! I almost forgot Joe Abbati. The soundtrack he did for Operation Body Count (1994) sounds a lot like dubstep nowadays.