To those who say these numbers can't be right don't underestimate the brilliance of Nintendo three pronged first half of 2008 strategy. They took GTA IV seriously as a threat, and responed by releasing their three biggest games of the year in a three month period spanning just before and after GTA IV's release. Smash Bros Brawl, Mario Kart Wii, and WiiFit are coming home for the Wii. They aren't stopping GTA IV from having massive numbers, but they are attracting many to the Wii who might have otherwise went for a PS3 or 360. I think you'll see the bigger system selling effect of GTA IV in May, but both systems will still be trailing the Wii by a wide margin due to Nintendo's big three scortched earth strategy.

Well Gamestop themselves say the number aren't right.
They claim hardware sales doubled the week GTA4 was released.
And they aren't estimating based on random sample data like NPD, they know exactly how many units they sold...

You created your own thread and then posted this here?

As people have said (in the thread about this) nothing Gamestop said actually contradicts what NPD said ...

And how do they know what the vast, non-Gamestop majority of retailers sold?

Gamestop statement is fairly consistent with the NPD results.

http://www.vgchartz.com/forum/thread.php?id=26962