Nahh you are reaching out dude, including prologue review proves that.

4 Gran Turismo games have a average of 93.52, 2 Forza games have a average 91

Its just basic logic, going by that the educated guess is GT will be of better quality.

Care to name any of these things that could happen between now and Christmas which could prevent GT from heavily outselling Forza?

GT getting canceled. Duh. :P

Haha, yep. That is the only thing.

GT5 First week sales will equal Forza 3's first month sales. I would be willing to bet on this with anyone.

Because the PS3 is in a place where it is said that Sony needs SOME genre where it still rules in sales and so on.  Gran Turismo has been the driving version of Halo.

In regards to the question, if Forza 3 does come out this year, I will say there is a good chance it will BLOW AWAY GT5 (full, not Prologue) by a WIDE margin THIS Christmas.  This is because there is a GOOD chance that GT5 won't come out this year.

I would say that the sales figures would be comparible of KZ2 to Halo 3 in regards to how it turns out.  In this case GT5 (full) would end up being like Halo 3, while Forza 3 is like KZ2.  Of course, it may be closer, if Gran Turismo is not longer all that, due to the extent the number of driving sims that have appeared.

Racing Games on the ps3 is like FPS on the x360 (sales wise)

FPS dont do as well on ps3 as they do on x360 even if they are better
so the same would go for racing games

Racing games just just as well if not better on 360 so no idea what your on about. :/

Disagree if GT5P is anything to go by. Graphics yes. Physics and gameplay no.

GT5 should theoretically sell more. However Forza 3 would be very close indeed. I am predicting GT5 to have the lowest sales of any GT game. Dont think it will be much past 6 mill for GT5.