I've got one: the 8th generation of consoles was more important than we realize it is currently.
It was the generation of learning many things - physically-based rendering, temporal antialiasing and optimized data streaming methods, to name a few. But there was a lot more than that which became not only common, but essential to that generation that's going to be expanded upon in the 9th generation of consoles. I oughta name some more:
Dynamic resolution setups
Image reconstruction, i.e. checkerboard rendering
Deferred rendering pipelines
Multi-core data handling to exploit higher core counts over raw power
Just to name a few off the top of my head. As a matter of fact, I don't think we've had a generation of learning how to utilize hardware in such an efficient manner even when comparing the 8th generation of consoles to the 6th generation. Boil most of the techniques used to get games running good and/or looking good on those consoles down to the core and the remainder of what you have is relatively simple: reducing geometry counts, rendering at lower internal resolutions, lowering texture resolutions and sacrificing audio quality. The 8th generation went far more into preserving all of the above while trying to preserve image quality too.