The Price is Right
Wheel of Fortune
Jeopardy!
Who Wants to Be a Millionaire?
Millionaire is mostly there for being insanely huge when it started, and being one of the most (
the
most?) internationally popular game shows of all time. The other three have been around forever, and are all wildly influential and referenced, parodied, etc.
I will also admit, I thought of this almost entirely from an American perspective. Jeopardy is the fairly expendable show here from an international perspective (unlike the other three shows it has hardly any success outside the US), though it has been referenced in many works that are internationally popular.
Other shows I want to mention: Family Feud, Takeshi's Castle, Press Your Luck, Let's Make a Deal, Double Dare, Legends of the Hidden Temple
Born to lose, live to win!