sporting skills aren't really as useful in the real world as mental skills are, especially in the information age. One of the jobs in high demand right now is programming, along with a lot of other degreed jobs in the IT fields. Sure, physical training does have its uses, but overall the brain is more important. Note I am not saying to play games all day, you should still get some exercise, but in accordance with today's world knowledge is more important.
Now as for the child's mind it depends on the type of game (remember that no game is equal to another, and saying so is like saying swimming is the same as hockey). If you give a child a game like halo or GTA then sure. But there are other games like Trauma Center, Pokemon, and professor Layton that rely much more heavily on strategy and text, extending problem solving skills and vocabulary.
Social networking is how a lot of people meet nowadays. Facebook, myspace, youtube, eharmony- those are all social networking sites. I have known people who have met and gotten married through game networks, people who have joined organizations, run businesses, and get jobs through social networking. Though you should still talk to people IRL it is not something that is so limited to a fantasy realm as you seem to think it is.
Laziness of children deals more with parenting I think than the games. Anyone can set a personal limit to themselves on it. Seclusion isn't complete either, as IRL tournaments of anything promote interaction. I have really nothing to say about senses, though games use visual and audio clues in them.
and thats my counter statement.