The first few posts nailed it Spec Ops: The Line and Dark Souls are two of the darker truly quality games at the moment. Spec Ops is basically Apocalypse Now re-re-redux and Dark Souls is... a unique beast that lords over Skyrim. Between Spec Ops and Dark Souls, Dark Souls definitely has the higher replay value, with an average first play-through lasting between 40-80 hours depending on how thorough you are, and if you run into much trouble with the difficulty curve. I would give Dark Souls (with the dsfix community patch) my highest recommendation just in general, but especially to someone looking for a very dark fantasy world that asks you to figure out the lore rather than spoon-feeding it to you like a child. It's one of the only games that I've played in the last 5 years that truly lived up to and then exceeded its reputation. With Dark Souls 2 on the horizon, this would be a good time to get the first game under your belt.