There are some genuine surprises and upsets in the results here - not least that very, very few games actually seem to utilise anything like the full power of the eight-core i7 5960X. By and large, it hands in showings commensurate with clock-speed as opposed to the number of cores, meaning that the performance profile of the $1000 CPU is almost entirely like-for-like with the far cheaper 5820K. But perhaps more surprising still is the showing of the 6700K. At stock speeds it's extremely competitive with the more expensive processors. Overclocked, it is the fastest chip in the line-up in all but one title - Crysis 3, where 5960X is faster.
The biggest shock comes from Far Cry 4, where Skylake positively annihilates both Haswell-E chips. We know that it uses one or two cores to power all of the others, and for this one title we see a 20fps advantage over the 5820K. Interestingly, despite the 5820K's overclock only being 200MHz higher, it achieves a full 10fps advantage over the eight-core 5960X. There are some other interesting results - Assassin's Creed Unity really looks GPU-limited here as none of the overclocks look particularly effective, and yet Skylake still manages to pump out a 5fps advantage. It seems that faster architecture can push the GPU limit a little further in a way that clock-speeds can't.
...The takeaways here seem pretty self-evident though - virtually all modern games utilise at least eight threads, and this translates into higher and often smoother performance when a Core i7 processor is compared to its i5 counterpart - in Skylake's case, the Core i5 6600K. However, we went into these tests thinking that the eight-thread support might result in even higher performance when run across more physical full cores. Crysis 3 and Grand Theft Auto 5 do show that there are some gains here, but they're quite rare - and they seem to be eclipsed by the pure single-core brute-force offered by a more modern architecture. In effect, the advantage that kept Intel ahead of AMD in the CPU gaming performance battle also serves to limit the effectiveness of the firm's own many-core designs.