i5 3570K is about 0~50% faster than i3 3220 depending on the workload, and in gaming it usually means 10~35% improvement, depending on the game and the gpu. The biggeest advantage for i5 K chip is the ability to overclock, and moderately overclocked the improvement could be somewhere between 15~50% difference. So, for gaming, I would say that 3570K is a much better choice, when the gpu is not the bottleneck.