Depends on your budget. Best right now is the i7-7700K but that is more expensive than the next step down.
Choices in the range of an i5-6500 that I would be considering are the i5-7600K and the Ryzen 5 1600X, bit more expensive but better gaming performance.
https://pcpartpicker.com/products/compare/8hwqqs,dQM323,VKx9TW,xwhj4D/
You have a real dogfight between these two with the i5 generally beating out the 1600X but not by much, usually 1-5 FPS. But in some titles you see big drops in the 1% and 0.1% FPS scores for the i5 compared to the 1600X, which is because of CPU loading (bottleneck). And this is the current state, should game developers start to take more advantage of higher thread counts the i5 will start to suffer. Because they are pretty much neck and neck in current performance, about the same price but the 1600X is more future proof that would be my choice. Feels so good to recommend AMD again, it has been so long. Not a fan boy, just hate lack of competition. But either CPU is a valid choice, Tom's still recommends the 7600K.
Here are the two paths
AMD
PCPartPicker part list:
https://pcpartpicker.com/list/9Jytbj
Price breakdown by merchant: https://pcpartpicker.com/list/9Jytbj/by_merchant/
CPU: AMD - Ryzen 5 1600X 3.6GHz 6-Core Processor ($227.99 @ SuperBiiz)
Motherboard: Gigabyte - GA-AB350-GAMING 3 ATX AM4 Motherboard ($101.49 @ SuperBiiz)
Total: $329.48
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2017-07-13 07:50 EDT-0400
Intel
PCPartPicker part list:
https://pcpartpicker.com/list/T92tkT
Price breakdown by merchant: https://pcpartpicker.com/list/T92tkT/by_merchant/
CPU: Intel - Core i5-7600K 3.8GHz Quad-Core Processor ($214.89 @ Amazon)
Motherboard: MSI - Z270 SLI PLUS ATX LGA1151 Motherboard ($126.98 @ Newegg)
Total: $341.87
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2017-07-13 07:51 EDT-0400