I just bought Just Dance 2 for my Wii today and I was playing up a storm. I've got a goal of 7000 sweat points this week and 1000 sweat points per day. I played my 1000 SP out and 10 mins-ish had gone by. Then I started dancing to some songs and BAM 40 mins had gone by. There's almost an hour dancing on my Wii :) Exercise has never been so fun!
I also bought EA Active 2 a while back when it was on sale. I played it over the last three days. It's pretty cool and with the workout routines it gives you, I want to go back for the achievement each day :)
Wii fit is of course good too but I'm mostly bored of all the games there so I'll likely just be on weighing myself each Tuesday to meet my goals on there.
I've also got Biggest Loser, DDR HP, and DDR HP2 for my Wii.
I've got a whole new list of Wii games I want now!!!