Generally speaking the recent the CPU architecture, the more likely it is to be more efficient and therefore able to provide slightly more performance at the same clock speed.
Dual vs. Quad... Generally speaking Quad cores will give you better performance, not because many games are optimized for quad core, but most games can take advantage of dual cores. Background processes can be taken up by the 3rd/4th core so that cores 1 & 2 can be devoted to gaming processes. That is assuming the games are programmed to efficiently use dual / quad cores.
Some games are more dependent on the CPU rather than the GPU. FSX and X3 - The Return / X3 - Terran Conflict are CPU limited. The X3 games are also single threaded so Dual / Quad core won't make much difference; assuming the same basic architecture, it is the clock speed that matters for the X3 games.
I suppose you are trying to find a review the following, but includes older CPUs and dual vs quad cores as well. Good luck find one...Intel Core i7-975 EE and Core i5-750 in Contemporary Gameshttp://www.xbitlabs.com/articles/cpu/display/cpus-and-games-2010.html