ZhugeEX on 05 January 2016
The PlayStation 4 sold through 5.7 million units during the holiday period (Nov 23rd 2015 - Jan 3rd 2016)
Here is some comparison data
PlayStation 3 in same time frame (2008) sold through 2.2 million during this same period.
PlayStation 3 in 2009 sold through 3.8 million during this period.
PlayStation 2 in 2001 sold through 5.3 million during this period.
