You might want to check out a band called "Therion". They're pretty much the pioneers of Symphonic Metal (what bands like Nightwish, Epica, and Rhapsody are).
Some samples of their songs are:
http://youtube.com/watch?v=Cg7DQcxvQWc
http://youtube.com/watch?v=d6h84W8qz0I
http://youtube.com/watch?v=_o6lX_qdlLI&feature=related
http://youtube.com/watch?v=jWYF8H_CDBY
Keep in mind because some of them are live the choir is toned down. On the studio versions they're much louder. Also, nevermind the video content.
If you enjoyed those, check out all of their post-Theli albums (which, if you're not familiar with their discography, would be:
1996 - Theli
1997 - a'Arab Zaraq Lucid Dreaming
1998 - Vovin
1999 - Crowning of Atlantis
2000 - Deggial
2003 - Secret of the Runes
2004 - Lemuria
2004 - Sirius B
2007 - Gothic Kaballah
)
In terms of VG soundtracks, check out the Chaos Legion OST.
Finally, in terms of individual songs to track down:
Basil Poledouris - Conan the Barbarian OST - Riders of Steel, Riders of Doom
Harry Gregson Williams - Kingdom of Heaven OST - Crusaders
Jerry Goldsmith - The Omen OST - Main Title
John Williams - Star Wars: Episode I OST - Duel of Fates
John Williams - Star Wars: Episode III OST - Battle of the Heroes
That's all I can think of off the top of my head. If you want creepy little children's choirs, too, I have an assload of Danny Elfman tracks I could recommend as well.
i liked some of basil poledouris's