Gold's Gym Cardio Workout for the Wii is a reasonably good workout game, but has several drawbacks. Intended to interface with the Wii Balance Board, Gold's Gym offers exercises for the balance board, but they don't work well and end up being more frustrating than useful.
The most entertaining and usable features of Gold's Gym are, unsurprisingly, the cardio boxing sections. With premade or customized workouts, you can produce a satisfying workout that fits your schedule, giving you a quick aerobic interval before work or whenever you have fifteen or twenty minutes to exercise.
The game takes a while longer to unlock than I'd prefer--I had to spend a few days going through the tutorials before I could actually get a good workout--but once this hurdle has been passed, the workouts proceed at a nice pace.
Recommended for increasing aerobic and cardio activity, but avoid the balance board options.