So, I was building a new pc for gaming and dev, but I can't choose which cpu to put in.
So I thought let's put it here: i7-7700k or Ryzen 1700X?

Your thoughts?

If price is not the problem, I'd go for the more expensive 7700k due to the higher clockspeed. That's something you'd notice more during day-to-day work.

I7

@TimoHo because adding more thread usually means more overhead as well.
Most game developers don't bother with writing concurrent code because it does not improve the game. The cpu is rarely ever the bottleneck.

The only reason you could use more cpu is if you want to run an ultra realism physics engine. In those cases developers start to really consider multi threaded applications.

TLDR;

Game development generally doesn't benefit from heavily multithreaded applications because there is no need for cpu power.