Soundtracks are some of the best music out there. I've been listening to them for ages. The first one I ever had was The Phantom Menace, which is absolutely amazing. Disregard the film, that soundtrack is great. Me and my friends were randomly listening to it this past weekend, actually. Still good.
Of course now I own all of the Star Wars soundtracks, and they're all fantastic. I firmly believe Star Wars is the greatest film score of all time, and the AFI agrees with me. I can never get enough of that. Empire's up there too.
John Williams has to be my favorite composer ever. I also have all the Indy soundtracks. Last year I was given a vinyl of E.T. (another one of my all time favorites). It looks like this:
Since then I've been semi-obsessed with buying vinyls firstly because they look great framed, secondly because I can convert them to MP3s, and thirdly because they're really cheap if you know where to get them.
In the past year, I have bought the following soundtracks on vinyl (with prices ranging anywhere from $.99 to $6.99):
Superman, Close Encounters of the Third Kind, Star Wars (because why not), Amadeus, Barry Lyndon, A Clockwork Orange (actually my brother got this for me when he was in Scotland), Butch Cassidy and the Sundance Kid, The Sting, New York New York, Julius Caesar, and Z.
All great.
Also, on CD, I have over the years amassed a wide variety including, but not limited to:
2001: A Space Odyssey, Boogie Nights, The Master, all of The Lord of the Rings, both of The Hobbit, a lot of Hans Zimmer stuff like all of The Dark Knight trilogy, Inception, Man of Steel, and Pirates of the Caribbean.
My second favorite composer is probably Ennio Morricone, so I got some of his stuff like The Good, the Bad, and the Ugly. An easy way of collecting good Morricone music is getting soundtracks to Quentin Tarantino films. I have Kill Bill, Inglourious Basterds, and Django Unchained. I also have Pulp Fiction, but that's Morricone-less.
I'm also a big fan of Bernard Herrman, but I don't own any of his stuff (been looking for vinyls). I do listen to him regularly on Pandora and Youtube, though.
Anyway, that's all I'll say for now.