Valve’s Steam has 40 million users (up from 35 million in 2010). It made Valve almost US$1 billion in games sales in 2010.
Microsoft has 40 million users on Xbox Live (up from 30 million in 2011). This earned an an estimate of over US$1 billion revenue from game, movie and TV show-related content in 2010.
I just thought it was an interesting comparison.