It definitely depends on the game console.
I have currently developed a fitness program that is strictly based from playing the Kinect, including the Biggest Loser game. Compared to other interactive consoles, such as the Wii, the Kinect by far gives you the ability to do full body workouts.
The Biggest Loser game lets you really target areas on your body. However, I wish it had the ability to accurately track your weight like the Wii does with a scale. Overall, I have found the Kinect to be a viable weight loss solution and replacement of a gym.