While this used to be true (and mostly still is), the tide is shifting on this point. Games are using more and more cores. Overwatch, for example, uses 6. I believe DirectX 12 makes it easy/reasonable to use 4 cores, with some benefit to be gained with up to 6.

Not that it really helps with some games. Dota 2 is CPU bound for the moment, so if you play that a lot then maximizing single-threaded performance is probably the way to go.

Still, if I was buying a CPU today, I'd be cautious about going for less than quad core if I was interested in new AAA games.

For sure at least quad core is a must, I just meant having 8 or whatever slower cores instead isn't (yet) better.

This is currently true, but I think this will change over time for two reasons:

1) Games are becoming less CPU-bound and are putting more work on the GPU, so the CPU matters less for gaming today than it used to.*

2) Vulkan and DirectX 12 make multi-threading easier and more efficient, so there is more incentive to adopt a parallel architecture with those APIs.

* Of course, I'm generalizing. Strategy games, for instance, are still very CPU-heavy and likely always will be.

Still, there's diminishing returns on more cores for such uses. You can use 2 cores, might use 4 cores, having 6-8 cores is probably just cause excess heat that could be instead spent to run 4 cores at higher frequency.

Strategy games can also be GPU intensive if they implement neural nets instead of heuristical models

they would be both cpu and gpu bound at that point :)

times are changing though https://www.computerbase.de/2017-02/cpu-skalierung-kerne-spi... (german, but see charts at the bottom)