After some recent benchamarks I've come to the conclusion that people really don't need to buy expensive CPUs or i5s and i7s to get the most out of their gaming.
Below are the 3 scenarios I tested.
Scenario 1 - budget gamer gaming on 720p-1080p on lower settings with a 100 dollar GPU
Test - AMD Phenom X3 8850 with a Radeon 7750 VS i5 2500k and 7750
Result - CPU bottleneck exists on low settings and 720p resolution but GPU is the main bottleneck when we go to 1080p. Furthermore, CPU bottleneck that I saw happens over 60 fps. COD4 for example at 720p was running 70 fps on Phenom and 120 fps on i5. Considering that 99.9% of the population use 60 hz monitors, you are not able to see framerate over 60 fps. So essentially its just a waste to disable VSYNC and game over 60 fps (unless you have a true 120 hz monitor)
Scenario 2 - mainstream gamer looking to run games at 1080p with a 200-300 dollar GPU.
Test - Overclocked Phenom X4 940 (3.6 GHZ) with a GTX 670 VS i5 2500k with a GTX 670
Phenom X4 cpu will bottleneck some games, compared to an i5 2500k. However it will do so well over 60 fps. You will get 90 fps + with a Phenom vs 150 fps with an i5 for example. But again...60hz monitor is holding your frame rate back to 60 and when VSYNC is enabled there is no CPU bottleneck.
Scenario 3 - Power gamer looking to run eyefinity, nvidia surround, 3D vision or resolutions of 2560x1440+. Price is not the issue.
Test - Overclocked Phenom X4 940 (3.6 GHZ) with a GTX 670 SLI VS i5 2500k with a GTX 670 SLI and 3 1080p monitors
No matter what game benchmark I tried, CPU was never the bottleneck. It is always the GPU. The moment you start rendering 2 or 3X 1080p resolution, the GPU starts to tap out before the CPU ever will.
Conclusion - For the most part you really don't need to shell out 250-300 dollars on the latest CPU if you want to have an exnjoyable gaming experience. You are much better off spending $100 on the CPU and $300 on the GPU than $200 and $200.
The old Phenom X4 CPUs are going really cheap these days and are excellent gaming CPUs.
Something like this in a gaming PC will last you for many years to come.