You might be wondering: why is the Intel i9 still the best gaming processor? Why are pro gamers like Ninja still using the 10-core 10900K when you could have a 64-core processor for AMD? And it is true that AMD's best processors absolutely slap Intel in terms of overall power. However, there is a very important reason why most professionals still use Intel.
The simple reason is: most games aren't optimized for more than 4 or 6 cores. If your processor contains more than about 8 cores, the extra ones aren't going to make too much of a difference. So while AMD's extra cores will be much better for 3D modeling, they won't make a difference in gaming. The difference between two 6-core processors will come with how powerful each individual core is. And this is where Intel shines: their incredibly high clock speeds and excellent thermals propel them above AMD, core-for-core.
The 5.1ghz clock speed is truly the best in its field, and Intel's engineers have also managed to shrink some components to allow 10 well-cooled cores to run with their admittedly chunky 14nm transistors (AMD's transistors are a mere 7nm). As Linus Sebastian (from Linus Tech Tips) noted, the i9 10900K has surprisingly good thermals because Intel's engineers were able to make some of the interior components much smaller than in AMD's processors. How do we know that the 10900K has much smaller interior components? Well, since AMD's transistors are half the size of Intel's, they should be able to fit twice as many cores. And that used to be true, with AMD's 16 cores in their Ryzen 9 3950X. However, now that Intel has 10 cores in their 14nm transistor, they have a disproportionate amount of cores.
Overall, we are not recommending Intel's i9, as it is hard to find and about the same price as the aforementioned 16-core i9. However, if your PC was purely for gaming, and nothing else, Intel still has the best gaming processor.