Roughly,
For most games (games prefer faster cores than more cores, Intel I5 8600k is better.
For games and for application which like more threads, Ryzen 2600 is the better option.
The difference is however not like day and night.
It is not really something you should be really regret or worried about if you choose any of those 2.
The most important stuff is ....really make sure you did your homework well on choosing the best priced 1070, 1070ti or 1080.
The most expensive 1070 is like the same as a mid-priced 1080, at least here where I live.
The best price/performance card I can find is currently the KFA2 1070ti EX. I do not know how the prices are on your part of the world.