Lakitu: it may have got lost in the other replies, but seriously, get him some melatonin. I know so many families whose lives have been revolutionised by supplementing this hormone that their children just don't produce enough of.
I'd be taking baby steps in your shoes. It is worth spending about 20 minutes a day completely on the agenda of one child or another, being with them, responding to what they are doing, playing whatever silly games they want, or just watching over their shoulder. No judging, no guiding, just connecting exactly on their level. At one point, you're there thinking "oh my God, this child could bore for England about this particular console game" and then after that you begin to look at it, and you see their passion, and you begin to appreciate their skill, and you can begin to build on that in the conversation. You can ask questions about what they are doing - they are working out how to answer them which, although it's fun, also breaks their monofocus on the screen. It gives you something to talk about with them when they are off screen, which makes being off screen easier.
It might take some time to build up trust between you.
Are there books or comics associated with these consoles? Spin off toys? Ways of creating models of the game characters in lego or blocks or something else? Imaginative games you can join in with which are all about these consoles? Can he start creating cartoons based on the consoles (I recommend GoAnimate), or working out how to put the theme songs into button bass, or anything else - it's totally worth encouraging him to develop that sort of thing. Watching youtube videos about the game is also a great way of moving through the levels faster and learning cheats (and before you know it he'll be on Minecraft via StampyBloodyLongHead like everyone else, and there's no denying the benefits of that game!)
And yes, it seems crazy from a top down, curriculum mentality point of view, but it really has been my experience that meeting a child in their obsession is a really good way of taking the anxiety out of it for the parent, and also helping the child to move beyond it into other activities WHEN THEY ARE READY (not on the parental timescale).
What's your long term goal? If you want to raise an adult who is immune to gamer addiction - serious addiction, I mean - then it might be best to be with him while he works out how to interact with gaming in a healthy way at a point where you are there to guide and help, rather than turning it into forbidden fruit which becomes a point of conflict through his teens.
Also worth thinking about the way that a closed gamer environment is actually a really safe space for children to be when they are children who are struggling with other parts of the world. There's a good reason why so many people on the autistic spectrum are gamer geeks - and so it's worth thinking about whether taking games away is actually the equivalent of removing a comfort toy from a child, or forcing a child with a broken leg to walk 2 miles without crutches.
I'm really just thinking aloud here, in case anything here is helpful. I should say: we don't limit screen time in my family, or only by being out of the house. The result is that each child has gone through a period (about a year) when they are very interested in screens indeed, and have got through that to a point where a screen is just one of the options - they are equally likely to be getting on with all kinds of other, more socially acceptable, stuff. They learned to be in control themselves; as parents, we just had to hold our nerve (and yes, bedtimes were a crunch point with one of my children for a while, and we DID have arguments over turning the computer off at bedtime, and I don't have an easy solution to that for you, but we did get through it in the end...)