BioShock is an entertaining game during the first few hours then the repetitiveness begins to get old and ruin the game
Weapons that you use to dispatch your foes sound, look, and act like they're from the time period of the 1960's. All of them are really balanced and do the amount of damage that you'd imagine they could do. In other words it takes more than a single pistol round to eliminate an enemy.
In addition to guns, the user also gets to use "plasmids". Plasmids are a gel like substance that the player injects, via syringes, into his veins to enable him to shoot things from electricity, fire, and bees at enemies. Plasmids are what make BioShock differ from most first person shooters. They also have a small role-playing effect where you have to decide which type of plasmid you'd like to stick with.
Graphics in the game are alright. Most of the time you'll be traveling through extremely dark rooms and water filled corridors. Rapture gives the player the feel of actually being in buildings underwater. Enemies for the most part look alike, and there aren't that many different types of them. The physics in game are realistic and the water effects are very pretty. You'll feel like your in an actual underwater city which is slowly falling apart around you.
Unfortunately, after the first couple levels everything that's so great about the game starts to become repetitive. There weren't enough kinds of enemies in the game. You can only kill so many crazed inhabitants, big daddies, and turrets before you start wishing your could shoot out the windows of the underwater buildings to kill some sharks, whales, or to just drown. Environments also become repetitive, with most of the middle levels looking the same, the developers must have enjoyed placing wood paneling in almost every single room. If you hate wood paneling on your walls prepare to be repulsed by BioShock.
Also, the game is short. I beat it in two days, where I probably spent around 5 hours each day playing it.
In conclusion, BioShock provides an interesting plot which will provide some entertainment until you finish the entire game. There is little to no replay value, unless you want to get all of the achievements or try to beat it on a harder difficulty. If you can avoid the repetitiveness of killing the same enemies in every room then you should consider renting the game.