I'm currently looking to build a desktop solely for playing World of Warcraft and Starcraft 2. I'm comparing an AMD 3.2 dual core and an AMD 3.0 quad core. I've heard these games run only off 1 core and that fewer more powerful cores would better suit my needs. Is this true?
I would second malmental's opinion. Buying an older C2D at this point is not a good investment. You would get much more bang for your buck, as well as possible future upgrades for reasonable amounts of money that do not involve replacing your entire mainboard, CPU and memory at the same time.
I say this as I recently transitioned away from two 775 systems (Q6600 and E6700) for my wife and myself. I went with a Thuban and upgraded her to a i7 920. To be honest, I have a hard time telling the difference performance-wise between the two systems, but it is a night and day performance difference from the old systems.
For your needs, follow malmental's advice. Balance your budget and get enough CPU for your needs. If you have room in your budget to go with an i5 760, then go with the Intel. If not, go with the AMD rather than going to any earlier C2D or C2Q solution.