John Williams
Jerry Goldsmith
Tangerine Dream
John Carpenter (the man who most influenced me to buy my first synth)
Bernard Herrmann (I have 3 CDs and one Album of his 1951 THE DAY THE EARTH STOOD STILL soundtrack)
Danny Elfman
Alan Silvestri (love the PREDATOR and BACK TO THE FUTURE music)
James Horner (especially early stuff, like STAR TREK 2 and BATTLE BEYOND THE STARS)
John Barry
Giorgio Moroder (CAT PEOPLE, AMERICAN GIGOLO, SCARFACE)
Christopher Young
Arthur B. Rubinstein (WARGAMES, BLUE THUNDER)
More recently, I have a strong fondness for the John Murphy's atmospheric style - 28 DAYS (and WEEKS) LATER and SUNSHINE.