Mark Morgan. Great mood, great sounds, simply GREAT in all ways:
http://www.youtube.com/watch?v=-0UrrVfYLBc&feature=related
http://www.youtube.com/watch?v=tliHaaziI_Y&feature=related
http://www.youtube.com/watch?v=UDSb4EwQCPg&feature=related
And here's the composer from Fallout 3. Hollywoodish string arrangements that could have been taken from some major action/adventure movie.(Some parts of the music is really good, but PLEASE, it does not suit a Fallout game. This track kicks ass but it ruins the Fallout mood... I feel more like it belongs in a WWII game or a Batman movie:
http://www.youtube.com/watch?v=eN0AE9lEruY