"Well the same would apply to a multi-platform game, but companies haven't found that not worth the effort. "
No, as I explained, that cannot be said for a PS3/360/PC multiplatform game. In most cases Polygon models and textures should remain approximately the same, even the shaders should be the same in most cases. Of course there will be adjustments but the hardware is just comparable. If you look at DMC4 for 360 and PS3 you will see, that they are almost identical.
That really cannot be said for Wii : (PS3/360/PC) Here you would need to redo everything.
You just have to look at Star Wars Force Unleashed, for PS3 and 360 and PC they will take the Havoc physics engine and their own interaction engines, for the Wii they have to develop a different version.







