What people need to remember.
Graphics wont be the only thing in the next gen which will scream out massive improvement.
You have to consider the scale of enviroments, detail, animations, and the fine details like a greater indepth of enviroment interaction.
Look at current gen and for example Gears of war, Epic tried to add destruction to the maps but they are more scripted than anythign else, imagine real time destruction and everything you can see is interactable destructable and movable, Ok there are many games what do have these features but not combined and no where near the quality of what we see in uncahrted 3 (graphics wise)
Lets look at l4d 2, graphics are no where near comparable to uncharted, but uncharted doesnt have as many moving object on screen (humans/Zombies)
Each generation upgrade isnt just graphics, its
RAM - more objects on screen, this can be from enviromental items to moving objects/humans vehicals etc.
Processing power - Gives them many object there own unique AI or physical effects. a can getting kicked will move, grass moving i nteh wind and getting crushed under your feet. Hair blowing in the wind Animation see link below.
http://www.youtube.com/watch?v=YEddrY0fA4Q <-- look at this as an example the technology is there, it can be done but combinign it with enviroments action etc is too much for current gen, these "finer" details are what will make next gen noticable.
The graphics improvement will combine all this together to give us a more fluid/realistic game even if the graphics dont look much better having the enviroment more populated with objects gives us the illusion of better realism, (Killzone/Uncharted use it to great effect) the object geometry are not actually very detailed go ingame go clsoe to objects and you can see this. but the way its all put together makes the enviroment look so good when you stand back.