I'm not sure what you mean about relevance, but I'll attempt to answer.
This thread is debating whether we should be appalled at China for this law, or whether it's morally similar to some of our own laws (like banning drinking and gambling for minors). Bogwog suggested the difference is we banned minors from drinking democratically, while China's "supreme leader decided he knows what's best". The parent to Bogwog's comment suggested they're similar and we're holding China to a higher standard (possibly due to our biases).
As you say, in both cases children under 18 aren't allowed to vote. That seems like a similarity between here and China. If children could vote here, that would strengthen Bogwog's argument.
(If it makes a difference, I'm against governments restricting minors from playing video games more than 3 hours per week. But I also don't think democracy is what would make it okay.)
A lot else could be said about this. Just to list a few possible objections to the democracy argument:
- It's kind of easy to just throw the word "democracy" around without actually establishing why the law is just and good and moral. For example, if a democratic country decided to ban Muslims, would people think it was moral and justified?
- Maybe the commenter feels democracy justifies it because the people (indirectly) chose the law. But in this case, the majority (people over 21) are placing restrictions on a minority (people under 21). That's a possible failure of democracy: a majority can abuse a minority, even if the minority is overwhelmingly against the proposed law.
- On top of that, most of the people being restricted (people under 18 or 21 depending on which law and which state we're discussing) weren't allowed to vote at all. They can't choose representatives in Congress.
- The comment overstates the difference between the US and China and makes it sound like this law is solely the whim of a dictator. While the US is certainly much more democratic than China, the US isn't completely democratic, and China isn't completely undemocratic. China has elections (https://en.wikipedia.org/wiki/Elections_in_China). Video game addiction is a popular concern in China. South Korea democratically passed a similar (though less severe) law restricting video games for minors. This is a position of the communist party, with a lot of public support, not just a personal whim of Xi Jinping. (People exaggerate how much China is ruled solely by Xi Jinping instead of the party as a whole. Xi is powerful, but he can be replaced by the party and he's only been leader since 2012, and no person governs alone.) Meanwhile, there are many reasons why US politics don't always perfectly reflect the will of the people.