So doubling their core count and disregarding power use and heat to hit 5GHz since Zen has launched is "hardly even trying"?
As to the original question, there are reasons to think the 9900k will be the best Intel has to offer for some time. 10nm on the high end is nowhere in sight. Will they make Sunny Cove on 14nm? Not according to the latest
leaked roadmap, which also shows 14nm all they way through 2020. When we do see 10nm, will it clock as high as a highly mature 14nm? Not at first, I don't think.
Intel also will have to give up its ring bus for the mesh at some point as core counts rise. Look at the power usage of the ring vs the mesh:
You're looking at about 8W vs 39W at 12 threads when you move to the mesh. That power will have to come out of the core power budget, meaning again likely lower clock speeds. AMD is already dealing with high IF power, but can get away with it because the Zen cores aren't as power hungry.
Finally, though this one is hard to say since data is scare, Intel may lose some performance in games when they increase the L2 cache size and change the L3 to a victim cache. The increased L2 offsets this in some games but others see performance plummet. Since there is no equal core count equal clock speed chips with both designs, this harder to say. Play around a bit in Bench comparing a 9900k and Skylake-x. Skylake-x is clocked lower, but not enough to explain some of the discrepancies.
Put it all together and I think the 9900k will be the best performing in games for some time. Can AMD match or surpass it with Zen 2? That I can't say. I think Zen 2 wins more of the non gaming benches and the 9900k wins more games than it loses.