Back when the Revolution was announced at E3 I, as a loyal Nintendo customer for 15 years, couldn't wait to buy one, Nintendo was always good at innovations, so what could go wrong? Well, as it turned out, lots of.
First there was the controller, which just didn't have enough sensory to make true 1:1 mapping happening, meaning all the great innovative games I thought of simply were not possible or would need to be scaled down to the point where they simply weren't interesting any more.
Secondly there are the graphics and CPU, I don't mind the lack of HD, but just shipping a slightly improved Gamecube in a new box doesn't cut it either. The Gamecube was in term of power for the money the best console hardware ever released, I expected the Wii to be of similar quality by *todays* technical standards, it however doesn't get close, no shader support, no anti-aliasing, etc. The Wii would have been outdated if it was released three years ago.
Third there was the price, I wouldn't even have minded if the Wii is being technically last-gen, if the price would have reflected that, but it just didn't. $250 for the Wii is ridiculous considering the Gamecube was $200 back in 2001.
Last not least, the most important aspect, the games. As before Nintendo completly failed to attract third party, after the N64 and Gamecube they should have known better, thats just inexcusable. Also Nintendo talked about "big idea being more important then big money" back at E3, today however the Wii is as close a platform as ever, neither is it open to indie developers nor does Nintendo actually support small games, PS3 and Xbox360 online shops are full with small games, both improved classics as well as completly original ones. The Wii on the other side only offers non improved classic, nothing original, no additions like network play and all that at a high price. And if that all wouldn't be enough Nintendo did their best to piss of Gamecube owners, not only was there support in the last years pretty substandard, they also delay Zelda:TP a year just so that they could hit the Wii launch, they also turned SuperPaperMario from being a Gamecube into a Wii game and who knows what other games suffered similar fate. If Nintendo would have wanted it should have been trivial to pack Wii and Gamecube binaries on the same disk to get a smooth transition, turning all those titles that don't make much use of the Wiimote into multiplatform titles, but they simply didn't, Wii titles only run on the Wii, even if they don't make any use of the Wiimote or that little bit of extra processing power. And if that would be enough, Nintendo also failed to have any real Wii titles ready at launch, those titles that made use of the Wii ended up looking more then techdemos then fully blown games, and even with Metroid and Mario on the horizon, I still miss that developed from ground up killer title that shows me that the Wiimote actually works. Wii Sports is all nice and good, but its to simplistic. Mario64 demonstrated what the N64 controller was build for, the Wiimote is still missing something of similar qualities and neither Metroid (lock on is still there) or Mario (mostly analogstick control) seem to make all that much use of the Wiimote.
So to sum it all up: The Wii turned from being a small, low cost, innovative console, into a high price, low-tech, recycle fest.