The reason price action is so great is because it is not some EA or fixed system. With price action, you are actually reading the behavior of the traders moving the market. Everything that traders are doing in their buying and selling is being represented right on the chart with price moving up and down, creating the price action story for you to analyze.
This is why you can read price action on many markets because all you are doing is reading the price action behavior of the buying and selling in the market.
Checkout the lesson; Stocks vs Forex.