In modern action-oriented games where players must visually track animated objects and react quickly, frame rates of between 30 to 60 FPS are considered acceptable by most, though this can vary significantly from game to game. Modern action games, including popular console shooters such as Halo 3, are locked at 30 FPS maximum, while others, such as Unreal Tournament 3, can run well in excess of 100 FPS on sufficient hardware.
Without realistic motion blurring, video games and computer animations do not look as fluid as film, even with a higher frame rate. When a fast moving object is present on two consecutive frames, a gap between the images on the two frames contributes to a noticeable separation of the object and its afterimage in the eye. Motion blurring mitigates this effect, since it tends to reduce the image gap when the two frames are strung together. The effect of motion blurring is essentially superimposing multiple images of the fast-moving object on a single frame. Motion blurring makes the motion more fluid for some people, even as the image of the object becomes blurry on each individual frame.
So it actually depends on you and the game you are playing. Some people say that you need a very high FPS count (>60) but that is mostly just to display what their pc is capable off.
You want to target a FPS count which you find acceptable or good and which seems fluid.