You see, now that's where I disagree.
I consider graphics to be what is actually rendered on the screen, and blurry low res textures, low polygon models, and a major lack of offtrack detail just isn't better in my book just because it runs at 60 FPS, or even 600 FPS.
GT4 fell short of Forza in many ways in regards to graphics. Fact is, you can take screenshots of the same tracks in both games, compare them to pictures of the real tracks, and GT4 comes up lacking. It doesn't even come close to the level of detail found in PGR3.
And just to make my point...
GT4:
http://games.kikizo.com/media/granturismo4_oct04/laguna_seca/dhw18.jpg
Forza:
http://www.xboxmatch.com/datamedia/653_014.jpg
Real Life:
http://felixwong.com/gallery2/images/laguna_seca04p.jpg
And although I can't do the same track, let's check PGR3 just for comparison's sake...
http://img.gamespot.com/gamespot/images/2005/319/reviews/927245_20051116_screen018.jpg
You would have to either be blind or severly biased to say GT4 looks the best.