Forza 2 is known for its suck graphics in reviews. GRiD is known for its excellent graphics in reviews.

Let me also say, DiRT isn't too far behind GRiD or GT5 itself. 

I hope GT5 gets a damage model,,,Casue I really can't play racing with out damage effects.

is there any word on possible damage effects for the GT5?

There is a rumor that they will be added, if they are, the frame-rate and that cherished 1080p could suffer. It's terrible imo, for a driving game not to have damage.

Let me do my comparison of non-cherrypicked screens:

GT5(60fps):

GRiD(Damage modeling/Cars get dirty):

The gameplay is also Arcade vs Sim.

Grid has pretty mediocre graphics, I really can't give it more than a 7 in that department. GT5 on the otherhand looks mind blowing.

Grid has nothing on GT5p, even the PC version can't stand up to it.

I think GT 5 Prologue can win by a decent distance, the amount of detail in the cars is amazing, hopefully the damage modelling will be just as good

Grid looks better than GT5: P but only on PC. But that can be said for any game. Overclock your computer to death, and any game can look better than even the most technically devastating of console games. Grid on 360/PS3 hold no candle to GT5: P though. Which is what we should be comparing.

Oh, geez who cares..
Even IF GT5P's graphics are better than other games', it will only be so for a short while until a game with even better graphics comes along.

Differences will be minor anyway, and invisible to anyone but the geekiest hardcore gamers. 

GT5P looks better and runs better, but that sprobably brcause ther eis less things to rendor on screen

GT5P has the best graphics of any driving game to date, GT5 will be king of driving this gen.