From Gamefly.com:

It seemed like the perfect idea: build a city hidden underneath the sea and populate it with a hand-picked group of scientists, artists, and visionaries. But when the experience goes horribly wrong, it's up to you to descend into the murky depths and decide what will happen to the mutated and dying population. Genetically modify your body throughout the city and upgrade your weapons using ionic gels, explosives, and poisons. Hack into computers to control this man-made world and give yourself an advantage over the enemy. Fight for your life - terrifying citizens lurk around every corner - and make your choices carefully, because each decision determines the outcome of the game.

Gamespot:

Socre: 9/10

While on the surface it might look like little more than a very pretty first-person shooter, BioShock is much, much more than that. Sure, the action is fine, but its primary focus is its story, a sci-fi mystery that manages to feel retro and futuristic at the same time, and its characters, who convey most of the story via radio transmissions and audio logs that you're constantly stumbling upon as you wander around. All of it blends together to form a rich, interesting world that sucks you in right away and won't let go until you've figured out what, exactly, is going on in the undersea city of Rapture...

 

IGN Review:

An intriguing, well-written story delivered with at a precise sense of pace. It doesn't get any better than this. 9.5 Graphics
The art style, animations, and special effects create an unparalleled sense of mood and believability. 10 Sound
Top-notch voice acting, spectacular ambient effects, and overall some of the best sound design ever built into a game. 9.5 Gameplay
Superb control, intelligent enemies, and a wildly entertaining mix of weapons and plasmids. 9.0 Lasting Appeal
A lengthy adventure, 20 hours or so if you don't rush it, yet there's enough variation in the gameplay to bring you back for another round.

9.7