Which processor is best for gaming: Intel Core 2 Quad Q8200, AMD Athlon X2 7750, or AMD Athlon 64 X2 5000+?

Any of these will be great for gaming , I myself prefer AMD but its my personal choice. Like Jr. said in his post worry more about a Video card then the cpu. I would also suggest making sure you have plenty of high end Ram too.

To be honest, I am an AMD fan/user myself. I have always been proud of the fact that the AMD chips were faster than their Intel counterpart. So when Intel came out with the Core Duo... I was surprised that they were able to beat the current AMD lineup. By "current" I mean what AMD has available in retail right now. So if you are planning to build your rig now or in the near future, I hate to admit it but Intel is tops right now. Me, I am waiting for what AMD is coming out with as a response to Intel's Core Duo. Basing on past trends, AMD is always able to come up with something better... (I do hope that that will still be the case this time around). At any rate, if what AMD comes up with is inferior to Intel's, then I can make the switch. So I will wait.

First off, Intel's Core 2 processors utterly smoke AMD's competing chips on performance. The Core 2 Duos dominate the X2 series, and Core 2 Quads kill the Phenoms. Only the Phenom II is competitive.

There's also roughly a 10% performance boost going from Intel's older 65nm CPUs like the E6600 and Q6600 to the newer 45nm CPUs like the E7200 and Q8200.

For gaming, clockspeed is more important than the # of cores, because most games aren't optimized for multiple cores. A 3.0Ghz Dual-Core E8400 gets higher framerates in games than a 2.4Ghz Quad-Core Q6600 - and costs $25 less!

So for gaming the sweet spot on price/performance is found on dual-core CPUs, rather than quads. For the price difference between a dual-core and quad core of equivalent clockspeed, you can upgrade the graphics card to higher model (which has a much bigger impact).

For video editing, 3D design work, DVD encoding the opposite is true- slower clocked Quads perform much better than Duos because those applications are coded to take full advantage of multiple cores.

Of the chips you've listed the Q8200 is the strongest performer- however for that price I'd recommend the E8400 or E8500 instead.

Just remember for gaming machines, your video card is by far the most important component. A system with a $150 video card and $75 processor easily outperforms a system with a $150 processor and $75 video card.

Technically 4 core are better than 2, that is if you are able to optimally tap the potential of all 4 cores.

I would worry about gpu more than cpu with regards, to gaming. Grab a better graphic card instead.