While graphics don't make r break a game for me (unless performance sucks), they are honestly a big thing when it comes to showing off a new gen.
I also disagree that diminishing returns is a thing. When Sony showed off Killzone ShadowFall, it was most definitely a massive leap in what we had.
I feel it will the the same, in relation to the SSD and just having more things happening.
When they showed it off, I didn't feel it, as the streaming quality was not quite optimal... When I got my hands on it it felt instantly that I plopped into next-gen. It was simply miles ahead of anything I had seen on the PS3 and the same is true for Ryse. I'm pretty much certain that's how we will feel when we get the first next-gen games as well. There are plenty of things to be improved technically and stylistically
And then there are the non-graphical aspects. Man, I used to be impressed by the crowds in Dead Rising on the 360. Then we had AC: Unity for the PS4/One. Can't wait what they will do on next-gen systems :D
Vote the Mayor for Mayor!