krik on 22 April 2008
Some data comparing NPD and VGC for 2008 I think it's worth sharing.
Wii:
VGChartz = 1,569,700
NPD = 1,575,179 (1,427,000 USA only)
Difference = 0.35% -> Right on the ball 
PS3:
VGChartz = 939,195
NPD = 887,480 (806,800 USA only)
Difference = 5.51% -> Over tracked by VGC buy well within the "10% margin of error" (51k difference)
X360:
VGChartz = 982,448
NPD = 821,260 (746,600 USA only)
Difference = 16.41% -> Way over tracked by VGC. A massive 161,188 units or 16.41% over NPD numbers.
2008 market share as per NPD:
Wii = 47.9%
PS3 = 27.0%
X360 = 25.0%
2008 market share as per VGC:
Wii = 45.0%
PS3 = 26.9%
X360 = 28.0%
Please feel free to comment and let me know if you find anything wrong with the numbers.
