The bar chart below compares the length, measured in kilometers, of the top 15 metro systems globally. In addition, the yearly ridership and number of stations are listed in data rows below the chart.
China has a clear lead with 6 cities in the top 15! In addition, Shanghai and Beijing have significantly longer systems than any others.

Bar chart comparing the length, ridership and number of stations in the top 15 metro systems globally
This chart was built with the Aploris add-in on PowerPoint for Mac 2016.