Honestly, I think High Voltage software's work on the Wii is an interesting contrast to Factor 5 and Free Radical Designs work on the PS3 ...
On one hand you have two established developers with a proven track record of developing high quality games who followed conventional "wisdom" and produced big budget blockbusters for the PS3; the scope of the project was too large, their timeline and budget were blown, and the quality and sales of the game suffered which resulted in the companies (essentially) going out of business.
On the other hand you have a tiny unknown developer who has mostly been focused on developing extremely low budget games on very tight timelines, who goes against conventional "Wisdom" and produces a more technically advanced "Core" game for the Wii. The overall result seems to be a game that is of decent quality and will most likely turn a profit; and more importantly for High Voltage (I would expect) it has given them the opportunity move themself out of the basment of the industry.
Now, as far as the Wii being "Underpowered" ...
A large portion of gamers still have very fond memories of (and some still continue to play) games from the Atari, NES, SNES, Genesis, Playstation, Saturn, N64, PS2, Gamecube and XBox along with many PC and Arcade games from the past 25 years. The Wii contains advanced enough hardware that it can duplicate and improve-upon any of these games and all it really takes is quality developers putting a solid effort into it.
Most people who complain about the Wii being "Underpowered" represent marketing for a company (who don't know how to sell a game without ever improving visuals) and people who develop the middleware that makes it possible to push new hardware to its limits. Most developers want an interesting product to work on and they don't (really) care that much whether they are developing for an iPhone, Nintendo DS or PSP or if they're targeting hardware that won't be on the market for a couple of years ... Certainly there is some value to producing advanced visuals, but there is also some value on developing advanced controlls.