If I take my friends brand spanking new gaming rig that cost a pretty penny the importants would be;
ASUS P8P67 Pro
Intel Core i5 2500k
Nvidia Geforce GTX 570
8GB GSkill Sniper series
Antec Gaming PSU 750w (modular)
Noctua NH C14 cooler
If you have similar and in some instances better, say RipJaws then you will likely crunch any game without the need to even OC.
My rig is a fraction of the cost and is just fine and dandy at handling games.
Gigabyte GA-P67A-UD4
Intel core i5 2500k
Coolermaster Hyper 212
Corsair GS 700 PSU
Corsair Vengeance 8GB
GTX 560 ti.