I've occasionally blogged about my love of movie music soundtracks as backdrops to my game, and I like to "tailor" that soundtrack by picking stuff that fits, is diverse enough to give a broad spectrum of sounds, yet which is unified at least enough by mood that it never feels out of place. I listen to this "soundtrack" while running the game, while working on the game, while writing stuff on the setting, while working on my novel set in the setting, and while generally tinkering with it in any way. After some time, I've decided that I've narrowed all my various soundtracks down to a few that encapsulate the setting as I envision it. I've divided it into "required" and "optional"--with the optional albums obviously giving a more full-bodied and diverse range of sounds and moods. Although since Hans Zimmer features so strongly on the list, maybe there's not a lot of diversity after all. And while I say movie soundtracks, and that's mostly true, there is one very notable video game soundtrack on the "required" list too.
In a real pinch, if you had to narrow it down to even fewer soundtracks, I'd recommend Red Dead Redemption, Pirates 2 (or 4), Prince of Persia and The Wolfman.
• Transformers 3 -- this actually sounds like it wants to be Inception. The two of them together blend pretty seamlessly into each other if you aren't paying attention.
• Batman Begins and The Dark Knight. I imagine when the third of that trilogy comes out, it'll be a good fit too.
• Stargate -- has great "adventure" themes, and a touch of dark Egyptian exotica that complements the Indiana Jones and Mummy soundtracks well.
• Last of the Mohicans -- although only the first nine tracks or so. This CD is bizarrely bipolar.
• A few other of the recent superhero movies have a nice dark action sound to them, and could be used: either Hulk, Thor, the Spider-mans, the X-Men movies, Green Lantern, etc.
• There's some other really good sword & sorcery like soundtracks -- the newer Clash of the Titans, 10,000 BC, Troy, Gladiator, the newer (or the older too) Conan the Barbarian, etc.
• Master and Commander
• The only point about adding too many of the optional soundtracks is that it starts to dilute the influence of the Required ones. I'd be very judicious about adding too many of them. In fact, I prefer to rip the entire desired soundtrack (as mp3 files) to a single CD-R, which naturally limits my ability to use too much, but also makes sure that it stays more focused on the "correct" sounds and mood.