Hell I'll make a prediction here.
I'll be using shipments since GT5:P is available for download and it's shipment+DL numbers are readily available from their site.
GT5:P will end up at 4.2-4.5 million shipped/downloaded by the end of the generation.
FM3 will end up at 2.7-3.3 million shipped by the end of the generation.
Keep in mind this is assuming they don't bundle the shit out of FM3.







