I would think of gaming less as a dangerous addiction and more as screen time. Assuming what he is playing is age appropriate, then in some ways it's better to be actively gaming rather than passively watching TV! He is at least using his brain and developing useful hand-eye co-ordination skills.
That's not to say it shouldn't be limited, especially if it's having a negative effect on daily life. i.e. Making him late for or being wound up for school, not doing his homework, rushing through a meal, delaying bedtime, etc. Think about what you would find acceptable if he was watching TV then apply that to gaming.
I wouldn't come down like a ton of bricks about his dangerous addiction. It's a hobby and a way to relax! Embrace it and gently manipulate it. If you can, learn about the games he's playing so you can have conversations about it - gets him away from the screen and interacting with you about a subject he'll definitely be interested in.
You could get him a gaming magazine to read. Depending on the games he's playing, you may be able to encourage him to draw/write about them. Maybe help him start a gaming diary, so he can log what he's been playing and whether he enjoyed it. Under very careful supervision, he could set up a review blog to share his thoughts online.
Perhaps persuade him to a youth group, where he might find friends to discuss/share/enjoy games. Challenge him to build Lego models related to the game. Make some gaming related cakes/cookies together. Think outside the box and guide rather than dictate, if possible! :)