Games depend most on the performance of a single master thread.
Few games can effectively use more than 2-3 threads.
Today, a I5 is about as good as it gets for gaming.
If buying new, today, I would buy the newest gen I5-7600K for gaming and plan on a conservative overclock.
As of 12/04/2016
What percent can get an overclock at a somewhat sane 1.40v Vcore.
I5-6600K
5.2 <1% delidded
4.9 14%
4.8 38%
4.7 67%
4.6 87%
I5-7600K
5.1 28%
5.0 52%
4.9 72%
As to Ryzen, wait for real gaming benchmarks. the 52% IPC claim looks impressive.
Not so much for 16 threads for the gamer.
Intel will not reduce prices of existing models; it has not in the past.
If faced with true competition, they will offer new models that are more price/performance competitive.
If the $100 price differential between I5 and I7 is not important to you, buy the I7, there is no performance downside.
Game developers want the largest possible market for their games.
No game developer will willingly undertake the extra cost to make their game multi core enabled and also require many cores to run.
They would not sell many games.