Honestly didn't even notice a difference when I switched from an i7-950 @ 3.67Ghz to an i7-4770k at 4.3Ghz. More depends on what GPU you pair it with and what games you play. Worst on the CPU for me is Battlefield 4, and it never goes above 45% or so usage.
Of course we are talking about tier 1, 2, and 3 processors, so not much room in the field. An overclocked i7-930 would be up around the tier 2 CPUs.