Not all games are made the same🙄
They are programmed/optimized differently😼

Programs need to be written in a way to split up tasks.

Imagine that to cook dinner one task is to wash vegetables, another is to chop the vegetables that are washed, third job is to fry the veggies, final task is to clean up. This dinner would run nicely on 4 cores assuming all 4 tasks were continuously being operated by 4 different people.

Basically everything will depend on the optimizations of the game itself. 6 cores seems to be "enough" for most games since they mostly aren't optimized to run on more cores than that

I'm hoping Zen3 will be better for games. I remember the 3900x did worse at some games than lower tier 3000-series because of the ways games handle threading.

Not at all. 8 cores is the sweet spot because consoles will be using 8 core CPUs, meaning that games will more likely be optimized for 8 cores than any other amount. 

8 Core will absolutely become the sweetspot this generation as the consoles move to 8 Good cpu cores instead of 8 ****ty jaguar cores which was a mistake last gen.

Depends on the game.

Alot of new and modern games are taking advantage of 8 core+, so the future is a high core count CPU with fast clock speeds. 

tasso11000
Alot of new and modern games are taking advantage of 8 core+, so the future is a high core count CPU with fast clock speeds. 

Source, or is this just speculation? I agree with you that 8+ cores will be the future, but it doesn't look like they're causing significant performance degradation just yet.