One game that Mr. Sawyer mentions is Electronic Arts' EA Sports Active. This game features a personal trainer who leads the participant through a workout that really makes the player break a sweat. This game encourages the participant to strengthen the upper body, build endurance, improve balance and strengthen the lower extremities.
During a recent "Wii-Hab - Using Nintendo Wii in a Therapeutic Setting" Seminar, a student was very interested in using Wii activities for high level patients in an outpatient occupational therapy and physical therapy rehabilitation setting. EA Sports Active provides high level activities that may be well suited for that population.