On my 3900X I've seen even single player action titles utilize 16+ threads with overall CPU utilization reaching peaks of 80-90 %.
Yes, it maybe be hard to parallelize game engines, but all major ones heavily use multiple cores. A bunch of years ago (4-5) people would recommend an i3-K dual core for gaming, because you could overclock it to 5+ GHz on air. That was sufficient for many titles back then. (And these i3s would sometimes give you higher FPS compared to the more expensive quad-core options). But a CPU like that is far too weak for newer titles.
> You still can't beat intel at the high end. Both in terms of heat and performance. If you have a task that doesn't parallelize well, you can't beat intel.
In terms of heat, that is, performance per Watt, Intel's high end is quite a bit worse than AMD's. It is true however that you can get slightly higher single-threaded performance out of Intel's highest-end CPUs, but not because they are more efficient (- AMD is better both perf/W and IPC-wise), but just by raw, unadulterated clock speed, pushing them to 5+ GHz. And that causes them to burn a lot of power.
Zen 2 has consistently ~10-15 % higher performance clock-for-clock compared to Intel's best while achieving approximately 60-80 % higher perf/W.
This LTT review captures the massive advantage Zen 2 has in efficiency: https://www.youtube.com/watch?v=ZYqG31V4qtA