From what has been said by several developers it costs between 1/4 and 1/2 as much to produce a Wii game that is similar to a PS3/XBox 360 game; on top of this, as you have commented on, many Wii games are much small in scope and might cost between 1/4 and 1/2 as much as a larger "High Production Value" game.
Now, with the success of the Wii it is highly likely that third party publishers will target the Wii with (at least) equal resources to the PS3 and XBox 360. I personally expect that this money will be split between "High Production Value" games and the type of Wii games we have seen todate; if these resources are split equally between the scales of games you could end up seeing a similar number of "High Production Value" games (or potentially twice as many) on the Wii as are being released on the PS3 and XBox 360.
Will this shift happen immediately?
Certainly not, it takes much longer to develop one of these "High Production Value" games than it does the types of games we have seen so far; on top of that some publishers have not accepted the reality of the situation and are arriving to the Wii very late.
