These are the PC specs advised by developers to run at minimal and recommended settings. Those requirements are usually very approximate, but still can be used to determine the indicative hardware tier you need to play the game.
Minimum system requirements
Recommended system requirements
Graphics card: NVIDIA GeForce 7600 or ATI Radeon X1650 XT or better with 256 MB
Graphics card: NVIDIA GeForce 7800 GTX or ATI Radeon X1950 XT or better recommended with 512 MB