Ryzen is a very good all round CPU but for gaming the 7700K is still the best. I suspect the 8700K will trump it shortly though. Or will it?? Could be slightly slower cores so perhaps it won't. Interesting times in the CPU world. I like it, the selection we have to choose from is getting better by the day.
Well, if you look at it, the 8700K probably won't overclock as well (more cores, more power needed, more cooling needed, therefore less headroom) and will probably have a marginally higher core-to-core latency (ring bus bullshit), which seems to matter in some games, so in games that only scale to 8 threads my guess is that the 8700K will actually be marginally worse than the 7700K, on average, when both are overclocked as far as possible. The 500Mhz reduction in base clock is concerning.
But in games that do scale past 8 threads the 8700K should do better. It seems to me like we can already get a good idea of what games those are by simply comparing the 7700K to the 6800K (at the same clocks if possible). Obviously Broadwell-E is a few points back on IPC but it should provide a good idea of what titles we can expect to see the 8700K take advantage of all 12 threads.
Joker's video is the best I can find and I've never 100% trusted his testing methodology, and I also should note that this is 7700K at 5 Ghz vs. 6800K at 4.3 Ghz. But it seems to suggest that even games that are known to multithread well (like BF1) don't actually scale past 8 cores amazingly well, which doesn't bode well for the 8700K.
https://www.youtube.com/watch?v=VdVc8APD0ts
I'd be glad to be proven wrong, though.