There's a million ways you can get into game development work, and rarely is a game made by one person. You can be a graphic artist, musician, programmer, advertiser, producer, manager, the list goes on and on. These are all just as valid careers alone or within any industry as it is with game development and rarely you're asking, "how much do I make when the film is done." so much as how much was I commissioned to do this or how much am I paid per hour. Because of this, education can be anything from a highschool drop out to a PHD.
I definitely wouldn't dissuade him from going into the gaming industry if that's what he wants to do so long as he understands that an idea does not equal profit. Negative reinforcement on people's desires is just a way to make someone unhappy thinking what they want is "wrong" or just set them back farther when they decide push away and do so anyways, so long as what they're trying to do isn't crazy. Almost no one in this world gets paid simply for ideas but just like any art medium there's a ton of work to be involved for every part of the process. Few people write, direct, act, record, edit, pitch, market, produce and sell a film in the same way few people do the art, music, programming, marketing, beta testing, producing and selling of a video game. It's a very serious industry. While I work a more typical 9 to 5 job, my wife is a freelance artist and programmer who prefers doing work with video game development and it definitely brings in good money doing so. As far as I can tell she's quite happy with her job and money hasn't ever been a problem, but I have no personal experience actually working within game development directly.