there really is no standard. an averagish sort of rig (as in what probably more gamers have than anything else) would be something like a 3200+ venice and 6600gt.
it would be more of 1GB corsair valueselect, 3200+ or most people are going with the X2 3800+ or a 3700+. 6800GS 7800GT video card. Antec treupower 550W power supply. MSI mobo or DFI mobo`