Meaningful to one's self and principles. In the sense that Viktor Frankl wrote about in "Man's Search for Meaning." Wherein he describes the survivors of the nazi concentration camps were the prisoners who had something personally meaningful to live for. People thrive if they have meaning in their lives.

If you can derive meaning from your career, that's great. Otherwise, family or contributing to society or whatever you think makes a difference in the world and is worth working toward.

Like everything, gaming is great in moderation, but the gamer who does nothing with their life but game is probably going to have some regrets on their deathbed.

If the gamer is happy spending his time with his parents and games, it might well be that his principles are aligned around this social connection and activity. It is difficult for me to judge from a distance. Moreover, he might not have any particular principle for his life. I know plenty of folks like that.

You have also used another word - meaning. Is that a synonym for principle?

I am sure the gamer interacts with his parents. I couldn't find anything in the medical literature about excessive gaming either. It is quite possible that he may have regrets on his deathbed like most people. However optimizing your life for the thoughts you will have in your deathbed might not be a great tradeoff if it means doing work that makes you miserable for most of your life.