I dont want any part of the rest of this thread BUT
Now that I have an X1, I put the Forza 4 demo on my 360 against Forza 5. The difference was quite a bit more than I expected really. Especially in the lighting. I have two 27 monitors (although different brands, and one is 1080P and one is 720P native) so I even side-by-side compared.
I often go back to a post by Fearsome Pirate where he put the percentage "maxed" he thought each genre was on 360/PS3 (his basic idea being that in diminishing returns, many genres were nearly "maxed" already on PS3/360). Just for fun. Anyways I think he said driving games were 90% maxed on 360 in his opinion. Well, he would never say that after comparing F5 and F4. I'm not sure what the difference is but it's clearly a lot more than 10%. The 1080P alone is huge. Really impossible to even quantify such a thing but to me F5's clearly at least 30-40% better, I think some people (image quality purists perhaps) would probably argue a lot more.
This is the sort of thing you can compare in youtube videos but you'll get the much better effect of course in person, especially since YT videos can vary so much in capture quality, bit rate, gamma levels, etc.
All that said, I would agree that while the difference is huge, I can see how it could be tabbed as a lot less transformational than the PS2 to 360 transition. It's undeniable F5 is a whole lot prettier than F4, but I can see how some would dismiss it as just a prettier version of the same basic thing. Whereas the PS2 to 360 gen, was arguably a much more transformational gap. Well, you can even point out the resolution change. SD to 720P=huge. 720P>1080P= very nice incremental change, but not as huge.
Anyway I'm pretty impressed with Forza 5. The lighting is sublime, there's absolutely zero pop in I've noticed, and to think it's all at 1080P AND rock solid 60 FPS on a console known for it's 1080P struggles...I never thought of Turn 10 as top 1st party coders on 360, but they seem to be with this game. It's a really pretty game. It looks amazing on my 1080P PC monitor up close. And all that on a HD7770, laptop CPU, with slow DDR3. I also suspect if Turn 10 had access to near final hardware a lot earlier than many other (especially multiplatform) developers.