Depressing indeed!
edit: Apparently, the NWR author has made a mistake, which they unusually did not correct as soon as they realised it (and still have'nt)
Here is the statement from the author
Hey all - sorry for having the wrong year's numbers done for GameCube. It isn't 14.5, but rather 9.5 million units. Not quite as huge of a disparity compared to the Wii U, but still not kind of awful. Entirely a mental error and our fault.
So yeah
http://vgsales.wikia.com/wiki/Nintendo_GameCube
Regardless, Wii U sales are still behind the GC