I know the difference between right and wrong, When I play violent video games I know not to do what I am portraying. I learned from Fox News that video games can boost your reaction time up to 25%! I am 13 with a 3.9 GPA and I have seen no negative effects on me.
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 3.9 in middle school but I never studied for anything 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.
Your ability to achieve and maintain a 3.9 GPA speaks volumes. If the four hours you spend playing video games do not hinder your GPA nor your ability to differentiate between right and wrong, as well as reality and fantasy, then you should feel free to express your creativity through means that you enjoy. So why not play four hours daily? You still have a pretty kick ass grade in the end and moral intact.
I just graduated from high school with ease and I'm an avid gamer. You shouldn't worry, 4 hours isn't that much. Let's say 8 hours of sleep, 8 hours of school. That leaves 8 hours for you to divide between school and personal time. Let's say, in extreme cases you need maybe 2 hours maximum to complete whatever you have to do (excluding learning for tests ofcourse). Spent those 6 hours left in whatever way you like, you being happy is most important: enjoy your youth!
As someone who has a musculoskeletal disorder and who gamed excessively at one point I would say No Way! You never know when it will strike you and once you have it it never goes away. Research MSDs they are not fun and they are becoming increasingly common. MSDs have a very negative effect on quality of life, definately not worth it.