The future of Nintendo is making fat sacks of cash from selling games made in 2007 on hardware that would be acceptable tech in 2000.
The Wii mote and Nchuck would have been ahead of their time in 2000, and many experts have stated that the Wii hardware is superior to last gen machines, so the Wii's specs fall in line with the natural progression of console hardware advancement.
It terms of raw horsepower, is it weaker than the PS3 and Xbox 360? Absolutely. However, as a video game console, that does not make it technically inferior to the other two when you pause to consider the fact that some Wii games cannot be executed on the HD consoles. So the playing field, in that regard, is even.
The deciding factor, as always, will be determined by the software. The Wii has the most successful software at this point, some of which will make it to the record books. That said, the Wii's hardware can be perceived as being STRONGER than those of the other two on the basis of its compatibility with great, successful software.