I think the consoles have very different demographics and that's that. A CoD title on Wii can be profitable, no doubt about it, but the market for it is a fraction of that on PS3/360. The ratio between Wii owners wanting a CoD game and PS3/360 owners wanting a CoD game is huge.
On the flip side, look at the demand on the Wii for titles like Wii Sports, Mario, etc. and compare that to say Banjo on 360 or Ratchet and Clank on PS3.
The bottom line is that if you really had to chose where to invest, for a title like CoD it wouldn't be the Wii. This doesn't make the Wii doomed, but it does explain certain opinions and views of developers and analysts.
In reality, if it's profitable to add another 1.5 M units of a franchise on Wii to sales of over 10M on PS3/360 then hopefully developers will say why not and make such games available to those who would clearly like to receive them, but in terms of general analysis the much smaller Wii sales are going to be judged somewhat harshly (arguably incorrectly as this simplifies the demographic position).
Try to be reasonable... its easier than you think...
