My 6yro is a wildman when it comes to most of the Wii "active games" he gets pretty excited and jogs in place and is constantly moving - he gets fairly sweaty doing it, tho he is probably an exception to the rule.
When I was in school we had a lot of phys ed - everyday in grade school, 3 days a week in middle school, and high school. Now I think my kid gets 2 days of gym a week. Sure there is recess, but its in 15 minute spurts, or a 30 minute lunch where half the time is spent eating his lunch.