VG Charts reports that worldwide 4.02 million Wiis have been sold worldwide. The breakdown lists 1.45 million were sole in Japan and 1.53 million sold in America.
The coolest fact about these numbers? That's nearly half of the XBox 360's install base of 8.66 million. After only a few months Nintendo has nearly caught up with Microsoft! The PS3 on the other hand has not fared as well with only 1.63 million sold.
This is why you can walk into any popular home electronics store and see a pile of PS3s sitting on the floor yet the only Wii you'll find is the one in the display case.