Civ 5 runs on Mac and is the only game that matters.
Also there's indie shit like Undertale and Don't Starve that seem to constantly be out for OS X.
Also Portal/Portal 2, all of Telltale's games (The Walking Dead, Game of Thrones, Tales from the Borderlands, etc) all the Half Lifes, etc etc.
"Games" is pretty broad, that's half the problem.