It really depends on the games themselves with the CPU. Some games can only use four cores at a time, while others scale better. In my opinion you're best off with a 6 core CPU like the AMD Ryzen 5 2600 with a B350 motherboard, or an Intel equivalent. In my opinion you're better chosing a six core processor as while the games may only use four cores, this allows two available for other applications (such as Discord, antivirus or other things which you may have running in the background). It also means the PC might last longer where you can upgrade the graphics card further down the line, while the CPU will be able to keep up. You might want to consider the Ryzen 7 8-core processors depending on how much you want to spend. The Non-X AMD processors come with adequate cooling, but if you want to overclock your processor you will need a better cooler.
6GB of graphics memory should be OK, you'll need more graphics memory if you want to run at very high resolutions and higher graphics setting. At the moment, Nvidia graphics cards seem to be the better choice at the higher end (GTX 1070/1080ti), while the mid tier (GTX 1060/ AMD RX 580) is more competitive. If you're using a Ryzen 5 2600, I recommend the Nvidia GTX 1070. If you're using the Ryzen 7 processors, I'd recommend the Nvidia GTX 1080ti.
I'd recommend 16GB of RAM. AMD publish a "supported memory list" which you can check if you are using a Ryzen processor. For your power supply, you can use the tools by EVGA or Cooler Master to calculate what you need for your specific build.
For storage, I'd recommend using an SSD to install Windows onto, and a cheaper, larger HDD for data storage. 1]: [click here