I'm just not sure if the Gran Turismo name means anything to the average consumer at this point. There used to be a time when every racing game on the market was compared to GT, no matter if it was an arcade racer or a sim. Obviously the franchise is just as good today as it always has been, but I feel like the majority of casual players have moved on to other (worse) games.
I remember when Sega GT (the first big Gran Turismo competitor, for those of you who don't know) was launched on the Dreamcast back in 2000. Comparisons between the two were inevitable. Even four years ago when Forza burst onto the scene, GT was still getting a lot of publicity. Now it seems like the press just doesn't care. I don't know why, it's a series that has sold tens of millions of copies worldwide, and it still doesn't get the attention it deserves. I guess that the older things get, the less people seem to care.
On the other hand, GT5P - the game that some people call an "overpriced demo" - is already a greatest hit. So maybe I'm wrong...I really hope so.