I'm not a gamer, but my system would be a basic gaming rig.

AMD FX-4300 (High end Quad Core)
8GB RAM (Many Core 2 Duos won't run this)

Throw in a GTX660, and you have a basic rig that could play GTA V or similar games.

A Core 2 Duo would be at more at home with GTA IV, which was released around 2008 if I remember correctly. Core 2 Duos are available on eBay for less than $100. They're a good machine to check E-Mails and do the basics- a student or home office PC if you will. But, the prices are getting to the point where there isn't much profit in them. I'll sell off what I have, as I'll still do well on them. But, they'll be the last batch. An early i5 or even i7 isn't much pricier, and is a much, much nicer machine.