The Wii actually could be a decent system, hardware deficiencies aside. What with its absolutely massive userbase and market penetration, if NOA cared a lick, they could have cultivated an audience of people who buy more then whatever fad of the year they're pushing (exercise, party games, Wii-motion plus). The Wii could have been an alternative to the high budget, risk-averse games that are crowding the big consoles, it could have been a welcoming home to all the kinds of niche games that the Playstation used to house. With a little quality control, and hell, I dunno,
actual risks of some sort, Nintendo could have built and nurtured a diverse and unique game library instead of the shovelware home the Wii has become.
I wouldn't characterize the Wii as so much of a failed system rather then a deeply disappointing one.
That is, except for when somebody (usually not Nintendo) does put out something that is totally fucking awesome (Tatsunoko vs. Capcom for instance), but those days are few and far between.