Imagine playing a game where instead of playing through it quickly to get to the next sequence or cutscene, it was actually worthwhile to just look around. To take a leisurely stroll through that world. To really be the character controlled by a joypad.
Bioshock does just that. From the moment the plane crashes into the water until psychotic mutants trap you in a room and are just waiting to break through the glass barrier, there is a complete immersion into the role given. The graphics are truly realistic, the gameplay timely and intelligent, and there is a thickening plot at every turn. This isn't just an adventure on the screen. It will pull anyone into it.