Doesn't everyone dream of stepping onto the pitch with the crowd screaming your name, and scoring the winning goal? Okay, there's a good chance you won’t be playing in the next World Cup, but you can still have fun trying. And football really is a fantastic form of general exercise.
Just find a group of people whose company you enjoy, and you'll have a great work-out. The aim is simple. The tactics are simple. Everyone knows how to play. And everyone (well, everyone apart from the professionals, that is) knows the rules.