Good thread! It isn't a bad idea to have some off - topic ones around here.
I've always though that I'm a person with very rare musical tastes, I don't (with some few exceptions) like vocal songs, I'm more inclined to hear purely instrumental themes.
Other thing because I say this is because I don't have favorite music groups, I have favorite videogame, movies and series Soundtracks (and also some of their composers), which in my opinion easily surpasses many Albums of most known (and overrated) artists.
To put some examples, some of my favorite composers are Nobuo Uematsu, who composed the Soundtrack of all Final Fantasy games until X (where he only made some themes) and, most recently, Lost Odyssey music, Yuzo Koshiro (Streets of rage series and Actraiser Soundtracks are some his works), Alexander Brandon (Deus Ex Soundtrack, which has really cool electronic and futuristic themes) and John Williams (I think that there is not need to say why he is one of the greatest composers that've ever existed).
I'd like to share other themes of other great Soundtracks that I know, but to not make this comment too long, I will put some of my favorites of the composers that I just mentioned. Nobuo Uematsu:
"Roar of the Departed Souls" or "Howl of the Departed" (Lost Odyssey OST) Lost Odyssey - Roar Of The Departed Souls - YouTube Yuzo Koshiro:
"Fillmore" (Actraiser OST): ActRaiser Music: Filmore - Stage 1 - YouTube Alexander Brandon:
Title theme (Deus Ex OST) Deus Ex OST Main menu theme - YouTube John Williams:
Superman Theme (1978's Superman's OST) Superman Theme - YouTube
Well that's all, but maybe I'll post other themes later.