At least from my experience of having a modern Core i3,Core i5,Llano A6,Q6600 and people I know with the Athlon II X4,Phenom II X4,Phenom II X6 and the FX6300,the Core i3 is more of a bottleneck in many of the modern engines when compared to the last CPU,the ones which will be use in 90% of most PC titles in the next few years. These engines will be used in a range of modern titles from FPS,RPG,online,games,etc. Major engines such as Frostbite 2,id Tech 5,Cry Engine 3 and Unreal Engine 4 are also designed to take advantage of more threads,and there are more which are doing this. Due to the consolidation of companies in the games industry you will see more and more games sharing common engines,especially with more and more PC exclusive franchises now moving to console too,and even the new generation consoles appear to be focusing on more cores but weaker ones.
Even Nvidia drivers now are designed to multi-thread better(not AMD ones apparently).There are better CPUs(Core i5) but the AMD ones are not some doomsay scenario with regards to gaming. So what I had a Q6600 too.