All of the choices that are up now; Metro 2033, BioShock 2 and Fear3 are great games.

Metro 2033

I haven't actually played this one, but I've heard great things about the gameplay and atmosphere. It's worth picking up at that price, but not worth your vote, because you can pick it up for 75% off over at GreenManGaming.

BioShock 2

Bioshock was the most atmosphere-filled game I've ever played. It kept me tense, while caring about all characters including enemies. BioShock 2 is also like this. I would say the plot and storytelling in BioShock is better, but BioShock 2 is also a fantastic game. Recommended for anyone who is a fan of shooters, good stories and settings in games and great atmospheres. As pointed out by a few commenters, you can pick up BS1 and 2 for cheap at amazon

FEAR 3

I was a fan of the original fear, I was a fan of fear 2. If you're a fan of any fear game, or if you've played one of them before, you know there isn't much 'fear' involved. The game doesn't get that fear comes from the unknown. The only way it will get you to jump is with a cheap scare that lasts about half a second. Either way, FEAR 3 is not that scary, but a good and fun shooter with some cool mechanics. Worth playing with a friend, that is always fun. Pick it up if you like shooters or are looking for some good co-op.

Sorry if these reviews or whatever you may call them were a little shit. All in all, vote for Fear 3, and spread the word that Metro and Bioshock are cheap elsewhere.