When I got in shape to join the military, I played Dance Dance Revolution just about every single day. We had just about all the PSX and PS2 games at the time, and we had Stepmania as well, with a USB/PS2 converter. I went down from 209 to 170 in a relatively short amount of time. I kept playing to maintain my weight, and by the time I got shipped to Lackland AFB, I was 166 at my weigh in.
Fast forward 6 years. I'm back to being out of shape, stemming from laziness, and I jumped up to 235. DDR is all well and good but it only provides cardio, it doesn't do anything else. I recently picked up the UFC Personal Trainer for PS3 and the thing is kicking my ass. The core workouts are intense, and the kickboxing training is quick and brutal. I constantly find myself sweating more then when I go to the gym or run. I'm on the 30 day workout, and finished Day 3 today, but I other workouts and exercises with it.
The problem with games like this is they don't control your diet. I'm back to my military fitness diet, which allows me to pretty much eat what I want, so long as I'm not binging. Drinking lots and lots of water is key, both for your workout and to speed your metabolism. In the military, it was 6 canteens of water a day. The other thing is to cut soda from your diet as much as possible. I always found it incredibly hard to lose or maintain weight while drinking any kind of soda. If I get fast food, I ALWAYS get unsweetened iced tea. It's just flavored water, it has no calories whatsoever, and tastes pretty damn good. Fast food is ok once in awhile if you are dieting, but just don't go insane and get it for lunch and dinner every day.