My husband wanted a Wii and got me Wii Fit in order to convince me that I wanted to keep it. And I will admit I had fun with it. Wii Fit holds you accountable and if you gain weight you will feel guilty, you also will feel guilty for missing days. But I had fun with it. You can choose what you want to do-Aerobics, yoga and I can't remember what the other two categories are. I believe one is balance (which I suck at). But I had a lot of fun.
I also loved the Wii Sports. I would run across my living room when I play tennis and baseball and I would yell at the little miis because my baseball team sucks. I also enjoyed the boxing so if you really get into it you can get a good work out.
I have a few other games that I like I just can't think of them. At the moment my wii is collecting dust because I am pregnant again and have been put on limited activity but I am looking forward to getting back to it after the baby is born.