If you consider the definition for fad like "A fashion that is taken up with great enthusiasm for a brief period of time; a craze." then you can easily consider all dominant consoles of their generation to have been fads ... The height of most console's popularity is only (about) 5 or 6 years, and after that a new system will come along and be adopted very rapidly and achieve similar heights of popularity.
Saying 'the Wii is a fad' as a negative towards the system only really demonstrates a misunderstanding of the gaming market and what a fad is.
Now, as for the calls about third party publishers 'commiting financial suicide' as Kenny put it ... what I think we have seen is many publishers are having difficulty adjusting to a market that did not turn out the way that they expected. Part of the problems they have is the difference in performance makes it difficult to switch the target platform of games mid development like they would have done in the past, and another part is that what makes for an interesting Wii game is different than what makes for an intersting PS3/XBox 360 game.
