According to the latest sales numbers of video game consoles in Japan the Sony PSP outsells the Nintendo Wii. Of course it is not a fair comparison as the PSP is a portable console and the Wii is a home console, but the Wii outsells the PSP in the U.S. by a huge margin.

According to the Enterbrain sales data the PSP sold 274,131 units in June and the Wii sold 235,990 units. The PSP also outsold the Nintendo DS.
In the U.S. Nintendo sold 675,089 Wii consoles compared to 182,300 PSP consoles in May. There is no June video game sales data available for the U.S. yet.
Via Reuters and Punchjump.

Photo:
Sony PSP Gadget Model. See more photos in the I4U Gadget Model Gallery.