One of the most radical changes to happen in the last two years in the PC hardware space has to be the launch of AMDs Ryzen processors. Despite the failure that was the FX-series with their Bulldozer architecture, AMD managed to shock the industry with the performance of their next generation Zen architecture.
After generations upon generations of consumer processors topping out at four cores going back to the Core 2 days, Intel finally launched their first 6-core processor for consumers with the 8700K almost exactly a year ago.
AMDs continued to persevere with the launch of the second generation Ryzen 7 2700X earlier this year, which managed to improve the single-threaded performance gap between AMD and Intel. 
Still, this performance gap existed, leaving room for what Intel is launching today, their first 8-core mainstream consumer processor, the Core i9-9900K. Finally having core count parity with AMD, and still holding an advantage in single-threaded performance, this launch has garnered a lot of attention.