That's surprisingly hard to answer, as I'm more familiar with individual cues than entire soundtracks. Having said that, there are two I have listened to all the way through and enjoy immensely. One is the soundtrack to Alien. The other is the soundtrack to Legend.

There are three things these soundtracks have in common: (1) Both are composed by Jerry Goldsmith; (2) both are for films directed by Ridley Scott; (3) both scores were heavily compromised for the final cuts of each film. In the case of Alien, many cues were either rewritten, shuffled around and used for different scenes, or altogether dropped. The remastered soundtrack from 2007 includes every unaltered cue, and while it's atonal and contains not a single hummable theme, it's a superb example of an action-driven score that establishes mood.

In the case of Legend, Scott rejected Goldsmith's score entirely for its American release, opting instead for a synthpop score by Tangerine Dream. When the director's cut of the film was finally released on DVD in 2002, Goldsmith's score was restored and was finally made available on CD to the American public. Needless to say, his is vastly superior to Tangerine Dream's. Listening to it is like being immersed in a fairytale, combining traditional orchestral elements with magical electronic effects.