Say what??? Not sure where you got that idea from but aside from CPU horsepower other factors that contribute to gaming performance are memory bandwidth, cache size etc. Look at the
benchmarks listed here along with some very good explanations of why the AMD chips, particularly the FX-55 and 4000+ with their higher memory bandwidth and larger L2 caches blow away the Intel chips in games like Doom 3 and Half Life 2.
You are greatly underestimating the performance of the CPU in gaming if you think that only the choice of video card makes a difference here as these test systems all used the ATI Radeon X800 XT with the Intel model actually having the advantage of PCI-Express and still falling way short.
This memory bandwidth and larger L2 cache also contribute to its performance in business apps, 3D rendering etc.
And I do have a nVidia 6800GT myself...
AMD 64 4000+
Abit AV8 Motherboard
nVidia 6800GT
2GB OCZ PC3200 Platinum Rev. 2 2-2-5
2 X Seagate Baracuda ST3250823AS
SB Audigy 2