boudy :
If you build a rig for the one of the most hardware intensive game, then you will be able to play almost anything else.
Precisely. Most people fail to realize this.
Okay, here's one. You didn't give a budget, but anyway.
i7 920.
Gigabyte EX58-UD3R-SLI (cheapest X58) otherwise Asus P6T
3 or 6 GB DDR3 1333/1600
Hard Drive- whatever you want. Velociraptor/SSD if you can afford.
GTX260 SLI/ GTX 295 (again cost is the deciding factor)
Antec 900
Corsair TX750
Any 24" monitor (if you're interested in Nvidia 3Dvision, get what they give you. Its a 22" Samsung 120Hz)
+1 for the above post again. Anyway, a 30MHz difference is not that much practically. You can say this is 700 and that is 730, but when you play, it might be just a 1-2 fps difference.