First, there are two Stargate SG-1 Soundtracks out there, one is just from the Two-Hour pilot film and this one from the first season. I've ordered the Pilot CD, but it hasn't arrived (yet).
However, the Season 1 CD has more variety since it is from several episodes. Its from GNP, the sci-fi soundtrack specialists. In fact, when I bought this CD it was priced promotionally by GNP with a Stargate SG-1 DVD.
This CD sometimes betrays the fact some of the instruments are synthetic, but it seems somehow appropriate for sci-fi.
More important is the music itself, which is often soaring and sometimes moving as it evokes scenes of struggle with the enemies rooted in Egyptian mythology. It is also skillful in its emphasis of wonder at the diversity of the universe.
It is the wonder at the universe and the spirit of discovery that is at the heart of the series (along with the wise-cracks and heroism of Richard Dean Anderson's character). This music is largely used as background but is certainly foreground-worthy and well above similar offerings in the genre.