I can imagine the way this movie got made was when someone with the production exclaimed, "Hey! Let's exploit the video game market! We'll sucker in teenage gameheads this way! We can make the movie seem hip by naming and showing shots of a lot of video games - that's cheap, and we'll probably get a lot of bucks from the product plugs! We'll also save a lot of money by shooting on location and at an actual video game festival instead of building our own. Oh, we'll spend a few bucks on some computer graphics, but only a few minutes worth - we can show clips from it in the trailers, and make the teens think the movie is all like that! And who cares if the computer-generated scenes are simply gratuitous flash? Who also cares if the final video game sequence couldn't possibly be believable as a video game? Oh, and the story? Well, we'll steal a bit from HACKERS - that's a Hollywood movie, so it must be good! We'll mainly steal the old story of the heartless corporation screwing over the little guy, with the little guy teaming up with his eccentric youthful friends to fight back and get revenge as well as fame and fortune! Though since it's familiar, I guess we'll have to make the main character so stupid that he signs a contract without reading it, and only makes one copy of a demo game! Other than that, all the standard cliches will be there! Plus, we'll make all the youthful heros annoying, because hey, youths are annoying, right? We'll speak their language, and make a fortune!"
From what I gather, GAMER didn't do much at the French box office. If you haven't guessed why, read the above paragraph again.