I have a bias towards better GPUs since I only have super high resolution monitors in my house, but even CPUs from a few generations ago are still perfectly viable for gaming if you have a good video card.
I still use a dual core E6600 overclocked to 3.4 GHz from 2.4 GHz. I've never had any problem running any of the new games I have at 1920x1200. I do plan on building a new computer this year with all the good stuff in it.