I wouldn't bother with an 8086K. It's nearly the same CPU as an 8700K, only at a higher price. And at stock settings, it's only slightly faster at single-core tasks, as the multi-core boost clocks are identical. At least the 9700K's multi-core boosts are slightly higher. In any case, I would be surprised if anyone could distinguish a performance difference between any of these i7s. So, the 8700K might arguably be "best" from a value perspective. Or maybe even the 8700 (non-K) if one has no intention of overclocking, since its boost clocks are only about 2% behind the 8700K, provided its inadequate stock cooler is replaced with something better to avoid throttling.
For something like gaming, unless you are already going with a very high-end graphics card, the roughly $100 difference between an 8700 and a 9700K would arguably be better put toward graphics, which will generally make a more appreciable performance difference.
What other hardware do you plan on pairing it with, and what kind of hardware are you coming from?