Hi awaywiththepixies.
It's so hard, isn't it! I too initially had such a strong aversion to the use of any sort of console or screen. Over the years, I have lost this fear and this, in large part, because I have seen way too many young people who I would have described as being addicted, maturing so wonderfully and simply thriving. ALL who have reached that age are either employed, or in uni and are loving life and giving back to it with joy.
I do think our fear of these media is analogous to the book burning episodes of yore. Any new means of passing on information is regarded with huge suspicion by those who are not familiar with dealing with the consequences. We worry about what will happen to the minds of those who are immersed in it. We naturally fear the consequences, and only hear about the possible terrible implications...as in the stories in the media which connect acts of violence to video games etc.
However, this last concern, I am fairly certain, is an error born of the availability heuristic. It is of course possible that I simply have the opposite availability heuristic, but I suspect mine is one that is born, not of recalling very rare, isolated, events, but one that actually more accurately represents reality. Instead of the incredibly rare occurrences, I have seen a pretty common-place group of mostly boys, though some girls who use these media extremely heavily, who have grown up to be wonderful, sociable, gentle, peace-loving, witty, sassy, worldly, competent problem-solvers who embrace stress when they need to and can multitask in a way that I envy profoundly!!
These kids have been HEd. They've played WOW, Runescape, Call of Duty, Doom, Rayman, Guitar Hero. They have laughed, written and talked about these games with friends and the wider world through online forums who have given huge dollops of critical feedback and who help to learn to think and write!
If a child is very absorbed in a game, you can be more or less certain that he IS learning something. It may not be a traditional form of education, but the degree of absorption is most likely giving him huge transferable skills.
My own son has huge skills in huge numbers of departments (having gamed heavily throughout his childhood). He has had virtually no formal lessons in anything other than music (which he chose to pursue). He is fit, takes his own fitness seriously. He is a gifted musician. Has just gone to college and is achieving top grades in all his subjects. He is kind and funny, (though his sister may disagree here...)
Other friends of his who did nothing other than play Doom until they went to college at 16 have gone on to win prizes at top unis, by which I mean to say that you won't be cutting off possibilities for your son by allowing him to pursue things that fascinate him, whatever they may be!
Ok, so it is very important you don't neglect him. You are meant to advise him as best you think you can!! Explain about the importance of exercise and offer him other alternative forms of entertainment. Most likely, perhaps with your help, he will see that sitting down beyond a certain length of time is painful and that he games more efficiently if he is fit and talks to others about it, gets their feedback, grows through learning to take criticism etc.
Books that discuss the future of education often talk about problems with the standard school model (shortfall of teachers, irrelevance of many subjects that rapidly become outdated, even within the space of a year!) These books are often explicit in their call to make education more like gaming.
I think the depth of attention that kids pay to these games, the complexity of the information they take on board, the speed with which they do it, the readiness with which they address complex problems...these are transferable skills and we can relax, if ever such a little, once we appreciate this.