At the current rate GT5 will outsell Reach (without digital sales)... there are more potential buyers for GT5 than Halo: Reach... in fact the XL Edition is not released in Europe yet (the biggest country for GT). In fact reach is more front loaded than GT5.
A little comparison:
GT5 2010: 5,264,164
Reach 2010: 7,100,482
GT5 2011: 1,786,379
Reach 2011: 1,594,218
GT5 2012: 307,832
Reach: 192,329
But if you add digital sales Reach will outsell GT5.







