Need more information. It depends on the game, the rest of your system, the resolution of your monitor......
Ok sorry i didnt include my specs before. My specs are:
Processor: Intel Core 2 duo E6750 @ 2.60 GHZ
RAM: 4 Gb
Monitor: Dell 22".
PSU: Antec 650w.
P.S: I prefer to play games at 1680 x 1050 but 1280 x 1024 is also ok.