A quick glance at my physique - not that I am suggesting that this is something you would want to look at, ever - will reveal that I am not a fitness expert. The ravages of time, sloth, and Cheetos have taken their toll on my mortal shell, and any efforts I make at this point are not improvements, but merely a reduction in the rate of decline.
In the process of trying to not die before I hit forty, I've learned that the most important part of any exercise program is not the equipment. It's not the type of exercise you do, how often you do it, or what time of day it is when you go for it. It's not the gym or the clothes you wear or the quality of your running shoes. The most crucial aspect of any fitness program is enjoying it. Which is hard, because working out is usually a dull chore. If you find a way to love it, you'll keep at it even when you don't feel well, when you're depressed, or when the weather is nasty. People who maintain an exercise regimen for years are able to do so because they learn to like it.
Finding a good exercise program is then about motivation management. It's about trying to find ways to make yourself want to do it. You buy the gym membership, hoping the guilt of spending all that money will make you go. (Hint: Guilt is actually a terrible motivator.) You buy new running shoes and equipment to have something to look forward to when it's time to work out, but that only works until the novelty wears off. You buy exercise tapes, but you get sick of them after a while. You make little deals and promises with yourself, or set up a system of rewards, all the while hoping to find some magic combination of policies that will make you do something you hate.
So what you need is something that you can do for hours without getting sick of it. Something like (and I really hope you saw this coming) a videogame.
While I've often made fun of Wii Fit in the past, I actually think it's the best exercise equipment I've ever used. Treadmills are bulky, they don't offer much variety, and using them can be dull. But Wii Fit costs less than a treadmill, it's quite small, it offers a huge variety of types of exercises, and it can turn your workout into mini-games to keep things interesting. On top of this, it can weigh you and chart your progress. Sure, the Wii Fit trainer is a passive-aggressive little shit and the games don't hold a candle to mini-game titles like Mario Party, but it's still better than walking forward on a treadmill and straining to hear the television over the sound of the machine and your own desperate struggle for oxygen.
True to form, this one successful and innovative Wii title has led to a dozen half-assed imitators, cheapo copycats, and other cynical attempts to cash in on the Wii Fit success without trying to make a quality product. This is a shame, because I think Wii Fit is a good start, not a good end. This idea is ripe for evolution, and the copycats seem to be beating it into the ground instead of building on it.