Its very unlikely 360 is nearing some graphical limit. While there was moaning about GoW2 graphics vs GoW I think that was more down to high expectations. From what I've seen GoW2 will look nicer and will add more enemies and effects. I think initially too many people thought there was going to be a really big leap.
The PC is the only platform where you regularly see huge leaps as games are released that require higher specs and deliver more graphically - and of course PC's can (money permitting!) be upgraded to meet those requirements.
On consoles its all about learning how to use the available, unchanging specs to the max, and that can occur right to the end of a consoles life (look at God of War 2 and similar games late in PS2's life for example). It's like the old 'add 1 to the biggest number argument' - you can always add a little with another pass through the same engine code to tweak it further.
The 360 I'm sure can be pushed further than it has graphically, and so can the PS3 too.
When you get games on consoles that stand out early on - such as GoW on 360 or Uncharted or R&C on PS3 - I think sometimes people just expect too much from developers to take something that was already great and push it to insane levels.
GoW2 will look and play better I'm sure, and so will Uncharted 2 - but neither is likely to look 4 or 5 times better than the original (say going from Half Life 1 to Half Life 2).
You'd need more than better knowledge of the console and a better tuned engine to do something like that - you'd need higher specs and that doesn't happen on a console.
Also - gameplay people - gameplay! Graphics are nice (and I admit I love them when they look good) but if GoW and Uncharted weren't also a lot of fun to play (and I believe both are) then all the graphics in the world don't matter IMHO.
Try to be reasonable... its easier than you think...
