That's a completely stupid idea that will never work, as is obvious to anyone who's actually ever attempted to get people to do things. It fails on so many levels that it's not really even possible to write a concise, structured rebuttal of it. Off the top of my head:

- Too weird, most normal people won't do it

- Not everyone gives a damn about video games

- Too much of a financial risk for gyms to sign up to such a system

- Too much of a financial risk for someone to build such a system for gyms to sign up to

- Too difficult to get everyone to agree on a game

- Probably wouldn't make all that much difference to the total amount of exercise being done, as it would turn off as many people as it turns on

Basically, this idea could work, so long as it was effectively free to implement. So, by the time physical and informational resources are that cheap, do you really think that no one will have figured out something more efficient than gyms to work out?

Next: "How to make everyone happier: just get all the warlords to agree to peace."