This is something troubling that hasn't changed much since the release of the systems. But if you compare the game libraries of the Wii and DS to the PS3, X360 or even the PSP, we see far less narrative driven games on Nintendo's platforms. Even those very few that have some narrative thread are quite weak by any storytelling standard, even that of VG storylines. (Think Professor Layton).
Lately I've become quite a bit more accepting of casual games as I have become hooked on a couple of them on my DS and Wii, but I do find the trend of there being a lack of narrative driven games troubling. Is this simply a case of third party's still trying to find an identity on Nintendo platforms (which they should have by now on the DS) or is the whole casual phenomenon endangering the very future of narrative driven games on all platforms?