I have DDR and wii fit and I just wasn't able to workup a sweat. For cardio I need to go hard, and I just don't feel like i can achieve that in my living room!
However if you are doing it at a fast pace and it gets you sweaty and you do it regularly, it stands to reason that you'll get results. If you commit to doing 1 hour of DDR every day, you'll get results because you're burning cals!
So the question here is not what the games can do for you, but what you can do with the games....