A 3.9 GPA is good, really good. If video games don't interfere with your grades, then there is no problem with playing video games. It's good for relieving stress that academics cause. So if you can maintain your near perfect grades, then there is no reason you shouldn't be able to play games.
Video games are a good outlet for stress release and relaxation. If you don't release your stress, you could end up hurting others around you physically or emotionally. It's pretty much the exact same thing as playing sports for 4 hours a day except you can get fat from playing video games.
This sounds like an argument with your parents. As long as you do not become obsessed with, it it is ok. I have a little brother who has terrible grades because he plays minecraft so much, but since you have a 3.9 GPA, I think you are ok. If you are in middle school, know that things are a lot harder in highschool. And this also depends on if you study a lot and devote time to your schoolwork, or if you are just lucky or smart. I had a 4.0 in middle school but I never studied so I could goof off. In highschool, I actually needed to start studying some things, and I found it hard to suddenly study so much, so I only have a 3.8 GPA now (weighted). If you know that you will not become obsessed and can restrict your time playing minecraft if needed, go ahead. If you are already in highschool, you probably have good time management skills.
Why would anyone intentionally play that long, you don't experience actual human interaction. I feel like if there was a kid with a 3.9 GPA they wouldn't choose to seclude themselves from society and stimuli. Interacting with individuals is important as a teen! You make friends now that you will stay with through highschool!
I was a 4.0 student of the month in eighth grade and played more than my fair share of video games on weekdays (and at times play video games all day during the weekends). To be candid, Middle School was a bit of a cinch due to the few advanced class offerings. However High school is a much different game (no pun intended). With the addition of AP classes and extra-curriculars needed for college, games interfered too much with my life to a point I had to cut it out entirely. I wish I would have gradually played less if not forgotten entirely video games during my eight grade year.