The original XBox (2001) sold 16 million units in North America, and lets keep in mind MS pulled the plug on this system prematurely to launch the 360.
I think it's quite possible the XBox One outsells the XBox in North America, especially if it has a full five year life cycle.
The Wii U right now is trending a fair amount below the GameCube, which finished with 22 mill LTD. So no, the OP's assesment really isn't that far off.
If the X1 outsells the XBox (2001) in North America and the Wii U continues to sell below the GameCube ... it's very likely actually that the X1's North American sales will eclipse Nintendo's sales.
Nintendo is a great company, but the appeal of a Nintendo home console without a breakthrough gimmick like a Wiimote that brings in tons of new gamers is simply quite limited. MS has much wider appeal simply because they have much broader developer support, they're not dependant on just one company's games.
People don't want a niche library console, even if some of the games are truly great ... they want a console that plays a really wide variety of games from many devs, this has even been true of successful Nintendo consoles (the NES and SNES). They had more overall content than the competetion.
