Hi OP - I'm the GMU dad with a DS who graduated from GMU in computer science from the other thread. I have a couple of points to make so may not finish on this post.
Our DS is two years graduated so some of what I say may be dated so take it with a grain of salt.
Our DS's interest in game design started with manga and anime and art. That led to studying Japanese and taking all the computer courses he could. He is gifted at all of those skills but not the math component. And that makes a difference (see below).
So when the hunt for colleges began we studied everything online we could (Game Design was the hottest major in the United States that year) and found very few schools, then, that offered a double major in game design and Japanese.
You can readily find lists of the best programs on Google (I just checked). We looked at Drexel, USC, Carnegie, etc. We also toured some SLACs that had strong Japanese departments but weak computer departments (Gettysburg, Dickenson, etc.). There are many more programs offered now than back when we were searching.
GMU was the only school that offered both majors so DS applied and it was a one and done and being in-state Virginia we were thrilled.
We were asked by the chair of the department when touring if DS had finished calculus. He had not. Therein lies the rub. The other students in his program came in as true coding nerds. They knew everything about coding and he was behind. If you haven't had calculus and haven't learned to code I'm not sure I would recommend the major.
However, if your son loves math, as you say he does, then yes - encourage him and get him on a program to finish calculus by the end of the junior year so that when he applies ED, EA to Game Design programs, he will look serious. Any certificates he can pick up in programming or coding along the way will help him in any game design program and in the application.
As to GMU, DS got a BFA (bachelor of fine arts) not a BS in Game Design and Japanese. If he were to do it over he would have done a BS and mastered coding and calculus.
So I would agree with the person above about Computer Science as a major and perhaps game design as a second major or a minor.
BUT! Serious Game Design (which is what it's called at GMU) requires a lot of courses that CS will not. At first blush, you might ask "why" music theory. The answer is that the creation and production of any game involves a lot of artists: first the story arc (Literature and English classes); the language component (Japanese is good if you can master it, but it is hard to learn); animation (GMU has a major in that); music theory (because all games have music); modern art; film studies; Computer science, Game Creation, finance, etc. etc. You can find this online on GMU's Serious Game Design page. The concept is that game design requires the ability to work with a number of artists to come up with a popular game - so one must work as a team with all of these different artists to pull together a marketable product.
Computer Science is, well, computer science so a different major altogether. But the two do go hand-in-hand.
As to job prospects, GMU is very good at placement. DS has been working at Bethesda Softworks for several years now. The job came through GMU. He's happy and has had to work overtime (double pay) only a few times. But it is a solid 9-6 hours a day working in front of gaming computers. If you are not up for that, then a different major might be in order. The pay is not great but considering he's fully employed during this time of crisis, he feels very grateful. Or at least Dad here is. And he has health care and nice perks.
So if we were to start the college search all over again, yes, I would urge computer science, but since DD was never good at calculus, that would not have worked out well for him.
BTW, there are summer gaming camps at American Univ., which DS took and GMU offers its own. That would be a good way to test DS's interest over the next few years.
If you are in-state Virginia, as I currently understand it, GMU is the only public university in the Commonwealth to offer the game design major because the legislators are sending all the money to fund it at GMU. (The Commonwealth is working hard to grow and expand the offerings at the Universities where there is space and room to grow - so be prepared for constant construction at GMU - but the upside is that almost everything, including the computers and dorms, are new or almost new). Hence, no Game Design at UVA or the other universities.
The other majors that GMU does well are Computer Science, as discussed, Economics, and Engineering (another option for your son if he eats up calculus). BUT, the big major that I would encourage anyone to seriously talk up with their children is GMU's relatively new Cybersecurity major. Those kids can write their own tickets when they leave. They are snapped up at graduation and are often gone in a year because they keep getting better offers. That major dovetails nicely with other computer-related sciences. Most of the cyber-security courses are offered at the newish GMU campus in Manassas, which is REALLY state of the art. That's where the big bucks are now = cybersecurity. Regular curriculum courses would be offered back at the Fairfax campus but jitney buses run back and forth.
BTW read up on Mason Korea - a true "satellite" campus. it has become huge in computer science, game design, cyber-security, and other fields. Your son can attend there, as well.
https://masonkorea.gmu.edu/.
You also need to read up on VSGI - GMU's "Virginia Serious Game Institute". It too has many of the computer-related courses out at the newish Manassas campus.
https://vsgi.gmu.edu/. DS interned there during the summers.
My work on an advisory board was to meet with the big tech companies on the Dulles corridor and I-270 (like Bethesda Softworks/Zenimax, soon to be bought out by Microsoft) to see what needs these companies had. Many need "serious" games made, such as how to teach a difficult medical procedure. Also, the military needs games to teach how to land on an aircraft carrier. One time, Fire Departments came in to request simulation games, etc. etc. Also, these companies then hire interns from GMU during the school year and summers. Through that, I learned about the computer science offerings. The chair of the CS department, a woman professor, used to attend. I would say contact her but I checked last night and don't see her name listed in the department anymore so assume she retired. Anyhow, VSGI exists to handle those contracts (hence, finance) to make the serious games that those companies and governments need.
I'm sure I'm missing something but I'll watch here if you have any further questions.