A soundtrack can either make or break the atmosphere of the movie it's accompanying. These 5, I think, are the best, and really add something to the movie they feature.
5: First Blood (Jerry Goldsmith)
From the opening bars of Home Coming, right up to the opening lyrics of It's A long Road, everything clicks with this soundtrack. Even when Brian Denahey arrests Rambo, the music fits. One of Goldsmith's best (along with Star Trek: The Motion Picture), it's worth seeking out to also hear the instrumental version of It's A Long Road.
4: Star trek II: The Wrath of Khan (James Horner)
As mentioned in my post about the film, this is another soundtrack that just fits perfectly, from when we first meet Khan, to the penultimate battle in the Mutari Nebula, right through to the aftermath of Spock's sacrifice, there's no bum notes. A powerful score, perfectly executed.
3: Detroit Rock City (Various)
A KISS movie wouldn't be a KISS movie, without a rocking soundtrack to make every comedic moment go with a bang. From Foxy On The Run, to the title track Detroit Rock City by KISS themselves, the soundtrack does come as a bootleg with more tracks from the movie, as the original release only had a selection of the tracks. Out of the two, go for the bootleg. Plus, the US theatrical poster is much better than our one (which was pure bollocks!)
2: The Empire Strikes Back (John Williams)
The Battle of Hoth, the Deception at Bespin and THAT plot twist, ESB was, is and always will be the best Star Wars movie ever made. So, the best Star Wars movie needs the best soundtrack, and Mr. Williams came up trumps with this one from 1981. The first of the movies to use the Imperial March, it finally gave Darth Vader a theme to fear him by. 'You don't know the power...of the darkside!' We do now!
1: Flash Gordon (Queen)
Oh, come on. Why not? It's QUEEN, for shit's sake! It has the awesome Flash theme, The Hero end theme (which, has two versions. The second part, which is part of the Flash theme, has different vocal harmonies on the DVD end credits, useless fact fans!), the rather brilliant Battle Theme, and Brian Blessed with his 'Second Wave......DIIIIIIIIIIIIIIIIIIIIIIVE!!!!' over the top shouty voice on it. So, it's win-win all round!