Nothing can top Star Wars. Anything else is an incorrect answer.
Some other of my favorite scores are Aliens (Horner), Batman (Elfman), Brazil (Kamen), Dawn of the Dead (Goblin), Die Hard (Kamen), Doctor Zhivago (Jarre), Edward Scissorhands (Elfman), El Cid (Rozsa), Fight Club (Dust Brothers), Good, Bad, and the Ugly (Morricone), Jaws (Williams), King Kong (Steiner), On Her Majesty's Secret Service (Barry), Once Upon a Time in the West (Morricone), Predator (Silvestri), Punch-Drunk Love (Brion), Sea Hawk (Korngold), Searching for Bobby Fisher (Horner), Stargate (Arnold), Taxi Driver (Herrmann), Twin Peaks (Badalamenti), Usual Suspects (Ottman), Vertigo (Herrmann), Wyatt Earp (Newton Howard), and Young Sherlock Holmes (Broughton).
But my current favorite that plays nonstop on my iPod is James Horner's brilliant score to Krull. The opening track is orgasmic and it's a shame so few people have heard it.