This is a mom speaking here. Personally, I don't play many video games because they suck time, but so does the computer, books and television. I would have to agree with your brother that your screen time and his are equal time wasters. While you might be doing something creative, he is also using problem solving skills and the same fine motor skills you are using; and if he is playing on line is interacting with others while using those skills.
As a parent, I could all screen time as basically the same. That means your two hours on the computer drawing, and chatting is the same as his two hours of gaming. I can practically hear the "but, MOM" that would be heard if your parents were to say this. You're doing your relaxing your way, let him do his his way. If we all liked the same things, the world would be a boring place.
It sounds to me like you are an 18 year old with an obnoxious younger brother that you want to control. I'm the mother of a thirteen year old son...and I'm sure hoping the obnoxious part is temporary, but I can't see that the video games make it worse. Lack of sleep on the otherhand.....