Wow. This thread is really interesting because as a semi-serious gamer I never really found the Wii very appealing at all. Of course I still own one, but that's not the point.
I only bought it for Super Smash Bros Brawl honestly. That is the one and only game I have ever owned for the system.
I think the Wii really appealed to people who were not gamers before the Wii. I have to admit that there were a few parties that I played Wii bowling at.
Correct me if i'm wrong, but there were never really any exclusively exciting games other than the Wii sports that came with the console and Super Smash Bros.
As mentioned by others, I think true gamers saw the value of the PS3/Xbox 360 and never really took the Wii seriously.