As others have stated in this thread, the best option considering how close we are to the launching of 7nm from AMD is waiting for the Zen 2 arch launching probably April on 7nm. AMD is poised to get ~13% greater IPC over current Zen+ which will place them well ahead of Intel. Will Intel launch 10nm? Probably at some point. Will it happen in 2019? Doubt it. We know AMD will be launching because they already have engineering samples on 7nm. Intel has nothing on 10nm and some "in the know" are saying they are abandoning 10nm. Personally I think Intel hit a wall with iCore that they don't want to publicly admit and can't make the transition to 10nm without basically a whole new arch (which would definitely explain the delays, I mean 10nm has been "coming" for years now). Basically you can believe Intel propaganda that 10nm is coming with huge performance gains (which they have been saying for a few years now) or go with what is a 100% fact AMD has engineering samples of Zen 2 on 7nm and will be releasing next year with leaked performance gains of 13% IPC on early engineering samples.
If you need to upgrade now and can't wait six months or so then the best "bang for your buck", "performance for your dollar" for a pure gaming processor is the i7 8700K. It is reasonably priced (especially for an Intel processor) and its performance in most games will be the equal of the i9 9700K or i9 9900K with a little simple overclocking. Most game titles don't utilize more than 6 cores so the extra cores in the i9 series won't matter much in gaming. Right now the best pure gaming processor for the money is the i7 8700K.
Now if you also have workstation needs then the best overall processor (gaming, workstation use and price) is the Ryzen R7 2700X. Going with AMD now would mean that you can always upgrade to Zen 2 as it will still be on AM4. If you want to stick with Intel and just want a gamer you really can't do better than the i7 8700K.