I really believe nobody expected GT3 and GT5 to look as good as they did in the end (or will do in the case of GT5). Look when GT3 launched, there was NO other game on any given system being technically so impressive, it just looked out of this world. GT5 on the other hand is being trumped graphically by at least two games now (Crysis1 and 2, and before someone says this is not true, well you're lying, I've seen Crysis on the highest settings and oh my G...it looks amost next gen).
You cannot compare both, really.
Crysis is by now an old game and runs on a poor Crytek engine. I know the game looks damn impressive, but you need the most high-end hardware to run it smoothless on the highest settings. If you thought those were impressive, then have a look at the mods for the game:
For the sake of eye-candy, please watch in HD.
As I said, the game runs on an unoptimized engine. However, the Crytek engine did get improved a lot with Crysis: Warhead which offers even better graphics than the original Crysis, yet it runs a lot smoother. This is probably why the majority of modding in Crysis is done in the Warhead game.
I myself play this game on customized settings which are a duplicate of the highest settings, but without the hardware impact. I haven't touched Warhead since I still haven't completed the original game. (Some maps are so awesome I re-do some missions at least 3 times) The thought of Warhead looking better and running smoother is too much since the original title already looks so fantastic on my laptop.
Crysis 2 isn't going to get any better I think graphics-wise. I think they have rather put in a lot of time making the Crytek engine run even better on most systems since, let's be honest, Crysis hasn't been the best selling game since only a small group of gamers could even play the game. Now that it comes on multiple platforms I think Crytek are wanting to widen their fanbase by bringing out a well optimized engine that most of us will be able to enjoy. I can't even imagine how Crysis 2 can get any better since Crysis is the best FPS I've played. The multiplayer, however, wasn't as good. But I wouldn't be surprised if Crytek announced the delay of the PC version for 2 years because the sufficient hardware isn't on the market yet!
Anyway, I would like to add that PD have done an incredible job on GT5 if you compare to most of the other PS3 titles. It's amazing what they have managed to squeeze out of the PS3 if you compare its specs to the high end PCs of today. Same goes for their PS2 titles; I still, to this day, think GT3 is one of the best looking games for the PS2.