My favorite movie soundtrack is from Spirited Away. Lord of the Rings might be up there too. Otherwise I'm not big on movie soundtracks because most of the time they seem like just a random collection of obscure songs from whatever era they were made. Those that are made of up actual musical compositions often seem too tied to the events of each scene in the movie and don't make much sense as stand-alone music.
As such, the only two movie soundtracks I own are from Spirited Away and Lord of the Rings.