I used to loved GT's Nurburgring a lot, like A LOT. Now, I can't even look at it anymore, due to loving Forza 5 and Project CARS's Nurburgring more. Their tracks are laser scanned, full of life, beautiful, etc etc. That quality! GT5/GT6's Nurburgring is just too outdated and is now a "standard" track too me unless PD laser scans it.
I know exactly what you mean and I feel the same.
My biggest issue is not the missing track objects or no 3d grass or the fact that is not so perfect as a laser scanned version (because for a non-scanned version GT's version is the most accurate of them all), my biggest issue is with the PS3 because the hardware is so old it cannot render high resolution textures, no dx11 lightning, absolutely no anti-aliasing and not a constant and smooth 60 fps (at least) frame rate.
I just took some comparison pictures between GT6 and Assetto Corsa, and because AC does not have it's laser scanned version of Nords yet, I took them on Monza.
You can see below all those missing things I said above, except the anti-aliasing which you can see it in GT6 too because I used the photo mode to export the pictures and when it processes the picture it adds anti-aliasing, so they look actually better here than it looks when playing in game.
AC
GT6 (photo-mode which adds anti-alising, it looks worse in game)
AC (close up pic with phone)
GT6 (close up pic with phone, in game, not photo-mode)
For me these are the major turn offs, the low res textures and horrible aliasing alone make it impossible to play this game anymore. Once you see the clarity and quality of a dx11 graphics engine with all the eye candy and anti-alising is almost impossible to like this old gen anymore.
I just came back after a few months of playing AC because their multiplayer is still in alpha and it's pretty bad at the moment, so I came here to have some MP fun on Nordschleife, but I don't plan to stay long. The differences are just to big.
GT5/6 looks good for a 8 year old game (console), but for today is very outdated. For me it looks, like a pixel soup with vacuum cleaner sounds, compared to what their competition looks and sounds like. And I don't even want to talk about physics.
So like I said, they need to make a huge jump forward with GT7 from this and I hope they do it good because I'm willing to give them a chance if they pull it off and not make me buy a new wheel, like MS does with Forza 5.
P.S. I forgot to say, both Forza 5 and especially PCars look better even than AC does, so consider that too. AC still needs a lot of graphics and all sorts of other optimizations.