Hmm, first off, the Wii has a different appeal than both NES and PS2 and one also has to consider the relatively high sales of the competing consoles that will contribute to overall console market saturation over time, neither the NES nor the PS2 had significant competition, selling several hundred percent more than the other available consoles in their time.
There is also the point that the NES was the spearhead of the home console invasion, being the first home console with broad enough appeal to sell as much as it did (nothing before was remotely close and, no, we cannot say that the Wii is the same since it has yet to show that it will be able to beat PS2's lt sales significantly, such assumptions are premature) and the added factor of PC gaming taking a much larger chunk of the overall gaming market now than it ever did in the late 80's and early 90's.
Its a good OP, no doubt and I always enjoy TheSource's analysis but I think if there's one thing this generation ought to have taught us it is that you can't calculate and predict it simply based on previous generations and backtracking to entirely different times. Let us also remember that many of the analysis in here have been quite wrong before and often times people severely overestimate the hardware sale possibilities of the Wii (yes, the opposite is also true but being on the other end of a spectrum does not make you more correct).