Athlon 64's are much better performers in games then their Intel counterparts. But the CPU isn't the most critical component for gaming...that's reserved to the GPU. With the newer games coming out CPU's are becoming less and less of a bottleneck due to the fact many of the newer games are very GPU/RAM intensive.
Best advice to give, is go for the Athlon64 if you are gaming. You don't need an overly fast CPU, as it has been said games are now relying on the GPU more than a CPU. Say, a 3700+ Venice cored A64 would be the sweet spot between performance and price. That way you could spend more on the video card