I think a C grade is being too gentle honestly.
Nintendo is actually asking you to pay a chunk of money to use a device that won't help you shed excess body mass. This thing will end up in the closet of forgotten games in LESS THAN A MONTH.
Think back to when WII SPORTS, was hot on the market and everyone claimed they were losing pounds and inches by...*ahem*... bowling and tennis. Now I ask you to take a look at those same people today and see how much weight they've kept off.
Theoretically a game that has you moving, instead of sitting on your fat ass, should be able to help you lose weight... problem is, Wii Fit is just a balance board that doesn't support more than 350 pounds...most obese people weight plenty more. It keeps you nailed to one spot due to the neccessity of it sensing your movement.
A better choice for weight loss would be Dance Dance Revolution. I have UNIVERSE and UNIVERSE 2. I can honestly say that I lost 7 pounds the month I got it...problem is, I put that weight right back on when Call of Duty 4 came out.
The key to these games is repetition. You WON'T keep playing the same old game over and over if new music or new games aren't released for it. While the 360 features downloadable extras for DDR, the Wii does not for either WiiFit or Wii DDR Ultimate Party.
Without repetition, whatever you do lose will come right back in spades.
And don't get me started on the BMI that WiiFit uses for everything. I am 6'7 and as the review states, BMI doesn't discriminate Fat from Muscle. Its a poor calculation of the body if ever there was one. It needs an algorythm that calculates changes in waist/hips and body mass. Only then could this thing approach true fitness goals.
If you really want to lose weight, you don't even need to go to a gym...all you need to do is free up some time where you can WALK 5 miles a week with a huge bottle of water. That exercise is FREE and it won't clutter your living room or your closet.
Wanna lose waistline? DO SITTUPS...cost = $0
Wanna build strength and muscle? GO TO A GYM or better yet, get a weight set of 50 pound and 100 pound dumbbells. do 5 - 10 reps a day and slowly you'll be lifting them with ease.
But the true key to weightloss is to CHANGE WHAT YOU EAT. KFC, Mcdonalds and Taco Bell aren't part of a good fitness routine. Put down that cake frosting and those cheetos. You need steamed EVERYTHING and a diet of water cranberry/prune juice, whole grain and FIBER.
A gimmick like Wii Fit is nothing more than something to raise excitement for Wii owners who realized that 90% of their best games have "Mario" or "Zelda" or "Metroid in the title and they are never getting GTA4.