According to VGC Homefront has sold 1,131,127...
if we are talking games released before 2011 but hit a million during 2011 then
Dead Rising 2 hit 1 million 12 weeks ago
Just Cause 2 hit 1 million 8 weeks ago
Alan Wake hit 1 million (physical sales) 4 weeks ago
UFC Undisputed 2010 hit 1 million 10 weeks ago
As for games released before 2011 but soon to hit
997.68k and selling between 530-790 units over the last few weeks, so just 5 weeks at this pace.