I've had mine about a month now, and whilst I am presumably still in the 'honeymoon' period, I'm pretty convinced that whilst the novelty will wear off, the quality of games should more than compensate.
Take wii sports as an example. With very basic graphics, the game could easily just have been taken as an introduction to potential control schemes - with EA etc potentially developing each sport into an individual ***le.
What I've found, is that even as a free bundled ***le, there is actually a surprising amount of depth to the game, with the possible exception of boxing. At first it is obviously easy to pick up and play, but I am still learning the finer points of spin and control in most of the sports, and still feel there is a lot on offer.
Now imagine a game which focused on one sport and introduced better graphics and even more control variables and you have the potential for some very engrossing gameplay. Sure, the graphics will never be as good as the PS3 or 360, but the control has a lot of mileage still. It's not going to be as relevant for some genres, but I feel that if developers work hard to use the full capabilities of the system, the lifespan of this console could potentially be massive.