For some perspective, because a lot of people seem to need it, here's NPD data from November and December 2006:
Wii sales
November: 476,000
December: 604,200
Total 2006: 1,080,200
PS2 sales
November: 664,000
December: 1,500,000
Total Nov/Dec 2006: 2,164,000
It's easy to forget that the previous gen is expected to sell far better than the current gen during a system's first holiday period. Even the juggernaut, the Wii, managed to only sell a little over 1 million units in the US in 2006. Now for comparison (using VGChartz numbers):
Wii U sales
November (to 1st of Dec): 552,583
December (to 29th of Dec): 533,975
Total 2012 (to 29th of Dec): 1,086,558
Note that NPD doesn't follow literal months, and it takes December to be longer than November, so the Nov/Dec split is likely to actually look remarkably similar to that of the Wii in 2006. Note that the primary purpose of this post is to note the PS2 numbers, by the way - people keep comparing Wii U sales with PS3/360 sales, but they ignore the fact that the exact same thing happened last gen, too, with the Wii.
Now, turning to Europe, let's look at how the system is performing (and yes, it's not doing *great*, I recognise that):
Xbox 360 sales
December 2005: 443,074
Wii sales
December 2006: 697,443
Wii U sales
December 2012 (to 29th of Dec): 469,064
In Europe, the Wii U isn't selling as well as the Wii did. But it's not dramatically worse, and the Wii U is still outselling the Xbox 360 during its launch. Comparisons with PS3 are more problematic, as it launched in March. To make the point, consider that it sold 622k in March, but then just 198k in April. How do we interpret this? Suffice it to say, PS3 had the strongest launch, but it isn't obvious how it really compares due to the very different launch timing (360, Wii, and Wii U all launched in December).
Japan is also worth a quick look...
Wii sales
December 2006: 958,199
Xbox 360 sales (for comic relief :P)
December 2005: 85,023
PS3 sales
November 2006: 165,996
December 2006: 306,609
Total 2006: 472,605
Wii U sales
December 2012 (to 30th of Dec): 644,474
The Wii U isn't performing as well as the Wii did in Japan, but it's easily outpacing PS3 and 360.
In short, if you consider the Wii U to be a flop, you'd pretty much have to call the PS3 and 360 major flops. This isn't speculation, it's actual facts based on numbers. And when you consider that the Wii broke all sorts of sales records at launch, you realise that the Wii U is probably selling better than most previous systems other than the Wii.
