Total bummer - thanks for the replies. It's my children and their small, sticky fingers that like to manhandle the games - almost destroyed the WiiSports disk. I wish, at least that one, should come loaded on the console. Isn't it a universal disk that comes with the Wii as default anyway?
Teach them how to handle the disks properly. My father taught me not to touch the bottom of the disk. I haven't touched it since.