Symptoms include browsing abandonware sites like The Underdogs for anything pre-1990; finding excuses to boot into DOS mode and coming home with a copy of Daikatana under one arm and Battlecruiser under the other.
Note that certain older games, like Tetris and Breakout, are excluded from the effects of CGS. It's okay to play these once in awhile without succumbing to its influence.
"It's kind of fun once you try it."
"So is a crap on the sidewalk. Face it man, you have CGS bad."
"Hey, is that Daikatana?"
"Yeah, I'm coming down with Crap Game Syndrome."
"Burn it now before throw you down a well."