@Rajendra: I used square for the reason it forms developement budget. We'd have a box if we'd include advertizing and funny shaped objects if we'd cut "complexity" into different segments.
You may have asked the wrong question, about why Wii isn't getting games with short campains and high graphics, it's more like why PS360 are getting the games. In the same way the devs/publishers think that Wii owners don't care about graphics, they think that's the only thing that matters for HD console owners (notice how everyone gets shafted), when too much of the budget is targeted to the graphics. Of course, Wii will be getting those games too, now Conduit as an example (i'd recall it was kind of short), but since there's not much competition, it will propably pay off.
As for the games with relatively lower cost in graphics and higher in the complexity side, like NMH or the PS2 ports, they never were supposed to sell in big numbers. NMH has its artstyle, where you can have "bigger production value graphics" for cheaper, just like SMG has cartoony artstyle, whics saves a lot in costs. Ultimately, it's better to have more gameplay with lesser graphics, if the gameplay is good.
@Vagabond: Actually, since you mentioned Wiis tech, you can find what it's designed for from the power consumption level. Keep in mind that Wii and 360 pretty much share the same tech, with the difference that in 360 the tech is used to squeeze high performance out of it, while Wiis focus for the tech is to be efficient.
So, what you may want to say, is that the debate isn't about tech, but performance.