What exactly is missing graphically from this generation's consoles that matters?

[Scoobes]

Also, it may be worth looking at some DX11 game shots to get an idea of what to expect in terms of effects:

http://www.mycrysis.com/gallery/screenshot

This gives some clue as to what some of the new visual effects will add to games but this is still only Crysis 2 so this is likely only the tip of the iceberg. Still a lot more experimentation and optimisation to be done.

Also, old but might be somewhat relevant:

http://www.eurogamer.net/articles/2011-07-20-new-xbox-and-playstation-4-what-to-expect-article