jkteddy77 :
Remember they said in 2012 that games would start using the FX6300 and 8150's 6 and 8 cores.
Here we are in 2017, and only a few AAA games coming out today can fully utilize more than 4 cores.
If you're talking about 4 "cores" -> then you're right, but 4 thread CPUs (as in an i5 - no hyperthreading) is starting to become a limiting factor in gaming. The Ryzen launch has shown us just how big the gap is between similarly clocked i5 & i7s on many CPU dependent games. As a point of interest, the old FX 8350 is now actually slightly faster than a 2500K, and probably roughly equivalent to a 3570K over a wide selection of games these days, despite being significantly slower when they were released. . Two years ago i3s were okay for gaming, i5s were plenty and only people doing streaming or productivity workloads would be advised to get an i7, because the extra threads meant nothing for gaming. That's just not the case anymore.
Games are utilising more threads, and that trend will continue, it's just happening slowly. Having said that, there is no question that the 7700K is the premium gaming CPU right now.
OP -> remember that the much cheaper Ryzen 5 1600 costs less, can be paired with a cheaper mobo and OC'd even on the stock cooler, or with a cheap aftermarket cooler for ~200Mhz more, and games identically to any Ryzen 7. So for gaming only - don't consider the Ryzen 7, they're too expensive and no faster (for gaming). If you want to save some money a Ryzen 5 is a solid CPU, but the 7700K is better for gaming. Had you not bought your GPU already then a fairer dollar for dollar capacity would be Ryzen 5 1600 + GTX 1080 vs 7700K + GTX 1070... that's a closer decision. But given you already have the 1070, it's just a question of whether you're prepared to spend the extra cash on the superior Intel CPU.