If you really want to talk about the traditional gamer and the casual gamer that's fine, but they are all gamers. I know people who own nothing but party games for their Wii, but they still play it just as much as I play mine with the standard core games.
Also, there is certainly already a market for core games on the Wii. Even for 3rd parties. It's also clearly much smaller than that of the 360's at the moment, and much larger than the PS3's (which it should be given the userbase difference). Of course, to be fair, the PS3 can live off of the multiplats it gets from the 360 and its couple party exclusives. The Wii also to be fair clearly could live off of Nintendo games only, but it also isn't. There are numerous 3rd party successes on the system accross many genres and game styles.
