Are you sure you've been reading this thread? I posted links, and I'll do it again for you.
"Microsoftâs Xbox 360 is on track to reach our 2006 sales estimate of 4.5 million units in the U.S."
The 360 sold 610K in 2005 to the US per NPD.
That makes a total of 5.1 in the US per NPD. Argue with them if you disagree.