While not necessarily as training-efficient as your next Pilates Session, Wii Fit is fun for the whole family.
The game itself is split into four sections: Yoga, Aerobics, Strength Training, and Balance Games. My personal favorites are the Strength & Balance, simply because those are actually games, and crack me up every time. The Yoga & Aerobics, while not as comically pleasing, are very calming & your personal trainer (male or female, by choice) is great. If you happen to do a certain exercise incorrectly, or you just can't get the hang of it, they will guide you through & make sure you can understand everything.
All in all, Wii Fit is a very solid, and, at times, hilarious game (like during the soccer header game, your Mii has to dodge a hit in the face by a cleat or *random* panda head). The Balance Board is the easily the most innovative peripheral for the Wii, and will satisfy your every craving, from Ski Jumping to mastering the Warrior pose. (And for the record, my Wii Fit age is a resounding 21 years old.)