This is different for everyone, but most PC gamers consider 40fps to be the minimum with 60 being optimal.

But in games, individual frames are rendered one at a time so it's tough to get motion blur between them the games must run at a sufficiently high framerate as to simulate smoothness. This makes motion appear smooth in video, even with a low framerate. Wave your hand in front of yourself quickly and you'll see it. It's because in things like film, motion blur is incorporated to the filming, since normal cameras are somewhat similar to the human eye. ' Isn't it impossible for the human eye to see frame rates above 30 FPS anyway? 'That's a popular misconception.

I don't know about SC2, but for many RTS's you need that framerate in order to micro well. It's not about who has quad core and who doesn't, it's about how 60fps isn't possible at all. Odd how they purposely underdeveloped the graphics in order for more systems to be able to play it, and then basically guaranteed suboptimal performance with lack of multithreading support.