That CPU at that speed performs on par with an i3-2120, a CPU no serious gamer would even consider in 2013 (or 2011 for that matter). I you don't believe me, look at this chart;
http://www.cpubenchmark.net/high_end_cpus.html
The Q6600 is the 4th one from the bottom of the chart, scores 2962 CPU marks, I'm adding a generous 30% for the overclock, ~3850, even though it probably would score less due to it's limited memory bandwidth.
My brother still has the same CPU as you, but he's not a gamer, and he doesn't overclock. I mess with him regularly, about does it runs on electricity or does it have a waterwheel to power it, etc.
If you're still not convinced, download Passmark Performance Test, run it, and see how many CPU marks you score. My i5-3570K overclocked to 4.6 GHz scores a little over 9000.
What games are you playing? My guess would be older DX9 games if you are still happy with the Q6600.