The first thing to note about BioShock is the atmosphere it sets. Though I never really got scared playing the game, there was a certain feeling that anything can jump out at you. It feels like a scary up amusement ride. The game's soundtrack is to credit for all of this, as well as it's graphic style.
One thing that I like about BioShock is that there is no one way to play it. You have options. Would you choose to use guns only, or would you depend heavily on your plasmid attacks? Personally, I spent more time using guns than using the powers and I think I made the game harder for me as a result. The ammo is pretty limited and I felt that I could not let any bullet go to waste. Not to say that's a bad thing, because it added to the horror atmosphere of the experience.
There are moral choices in BioShock. You come across "Little Sisters" in the game and they contain the ADAM that you need to fuel you powers. You can choose to harvest the Little Sisters, which results to the death of the Little Sister but you get all of her ADAM. The second option is to rescue her, which leads to her living but you get less ADAM. Weather you choose to harvest or rescue the Little Sisters effects the ending of the game, which might be an incentive to play the game more than once. The moral choices, though simple and not-so-settle, are one of my favorite parts of the game.
My only complaint with BioShock is the game's pace. It's meant to be a slow game, but I felt at times the pace to be too slow and lost interest at certain parts of the game. The shooting also feels a little clunky, though I don't know if it's intentional to make the horror aspect of the game more enhanced.
Overall, I really enjoyed BioShock. If you're looking for a creepy, dark, and challenging game BioShock is a nice choice. Just be warned that the game's pace isn't perfect and it's not the best shooter mechanically compared to other shooters that are out right now. (4/5)