Intel's architecture is focused on better IPC performance which results into better single core/single threaded performance. AMD's architecture is weak in IPC which resulted into weaker single threaded performance.
For example, let's take the 4690k vs 8350.
It's like take 4 super cores vs 8 weak cores.
Games at the moment prefer stronger cores over weaker ones and FPS is more stable and higher on an i5.