I love my Wii Fit... (Plus, if that makes any difference). I've only just started using it so I can work out every day and I was surprised that I actually "felt" the work out. The problem if that's your only exercise is that you can create a "routine" but its only yoga, muscle strengthening, and balance. If you want aerobics, you have to pick a particular game and the up the minutes to make it worthwhile for a sweat. Regardless, I love it and do it every morning - even a bit on days when I'm going to the gym!
Exercise ALWAYS helps when losing weight and it makes you feel much better. Good luck!!