The Playstation / Nintendo 64 generation was a landmark breakthrough - suddenly 3D gaming on console was the norm.
The Dreamcast, PS2, Gamecube, Xbox generation was another, smaller, landmark - suddenly 3D looked good. If you ported a previous generation game to the new generation, you got instant results - your textures were perspective correct, you stopped having a lot of sorting issues, yada. At first, a developer could impress people without doing much, if any additional work.
You do a straight port of a current gen game to the new next gen - it looks identical. Unless you're hooked up to an HD TV. The burden is definitely on the developers to prove that these new systems are worth upgrading for.
I'd almost think that maybe this could be the generation where people wise up and realise - "Maybe I don't need a new game console" - but it won't be. We'll see massive marketing budgets. We won't be able to get away from the Xbox 360 and PS3 advertisements. People will buy these consoles like hotcakes without even knowing why they should. Or shouldn't. And someday there'll be a killer app for them, that isn't available on a previous console, and I'll have to buy one.