Dollars, euros, and yen are all just currencies you can price any asset in. Everything is cheap or expensive relative to the currency you hold.
Thus if gold is truly a world currency, then the S&P 500 index of U.S. stocks is dirt cheap when priced in it. For every ounce of gold, you can now buy more than five times the amount of stocks you could have 10 years ago, as shown below.
The tricky question is where this stocks-to-gold ratio will go over the next 10 years: