(Professional advice is always the best course of action - internet advice is always backseat to confirmed experts)
Hey OP - Im bad at structuring this topic so I'm going to free-associate my way to my point, hope you don't mind! I can identify. Went through a 5-year period that started out very similar to your bro and got as bad as I'd imagine this kind of thing can get. Unfortunately, addiction to video games/ addictive patterns of behaviour with gaming are issues that have only really been made possible recently and as such, research is still ongoing. Hopefully psychologists will soon be able to demarcate pathological gaming from an awesome pastime (that I still enjoy).
I'm delighted that your bro has skills and related work to support himself with. That's more than I had, but it does pose its own set of problems. Your brother seems to have a nominally adult life; he earns his own money and does not seem to materially impose on anyone/conduct himself as a dependent monetarily. I don't want to speak beyond scope, but I think this is kind of seen as a final obligation by young adults.
The idea in late teens and 20's Uni is that you do the study, get the work, earn the money - bam. Grownup. You're out in the world, beholden to no-one, taking bites of whatever size out of the proverbial oyster. In direct terms, people spend a huge section of their young life in an educational system being outfitted to achieve a specific set of goals, outlined above. This is, it has recently become apparent to me, not necessarily enough to structure a healthy, stable future.
People (or at least a significant portion of people) need to produce things to keep the machine running, and they're compensated for it. The production itself, which most education outfits you for, is not (for most) a sufficient endgame. You work to earn and then what else do you do? Scuba, travel, sing, look at shapes and colours etc. Basically, non-professional recreational goals. I think this is your brothers problem, if indeed he has one.
For some, gaming all day and earning achievements and exploring computer entertainments is a sufficient end-game. I think, from the tone and content of your post, that this isn't what you brother had in mind when he imagined his future as a kid. There's nothing prima facie wrong with it, it just doesn't lend itself super-well to a balanced lifestyle that includes your quota of exercise, ongoing intellectual growth, life-experience-gaining, and nearby non-familial mammal time. A large gaming pastime has to be balanced with other things and that is actually hard to do for quite a few people. Some people fail, and even assisted, some people (yo) come to gratuitous circumstantial harm before their life changes to respect lifestyle balance.
Finally, I think your brother has some responsibilities as a family member, as a housemate, as an employee etc. It sounds like he's not meeting those from your perspective. What do the rest of your family think (not that your feelings are illegitimate)? Are your concerns shared by them? I think you and others who may not be getting their reciprocal share from your brother and need to express the problems you have.
This doesn't need to be an exclusively "for your own good" type conversation - you and your family and his friends have needs too. Besides, whatever else the case is, your brother is a working adult, and whatever you and others close to him say or do or offer, the only thing that can possibly change your brothers behaviour if it needs to change, is your brother.
My advice - get together with others close to him, talk about the impact of your brothers habits on you and (if any) them. Work out concise issues to be expressed to him, and have a conversation with him. Find out if he has a problem with the way his life is. If he does, offer support. If not, and he can honestly tell you that this is how he wants his 30's, 40's, 50's etc. to be, and he plans on meeting future mrs.yourbrother (or mr.) this way, or that he doesn't want to meet anyone or do anything else in the future (which I find impossible to believe about any young man) then you have to be prepared for there only being so much carrot that can be offered. You won't be supplying he stick, he will, and there is limitless stick