Steam Usage Statistics Published
Ars Technica has published some research it did into the habits of Steam users in a report called Steam Gauge. Ars collected public data to analyze the playing and purchasing habits and some of the findings should be of no surprise to anyone that has experienced a Steam sale. The study found that 37% of games owned on Steam have never been loaded, remaining unplayed and in the users backlog. I would estimate that I personally have at least 100 games that I have yet to play, all the result of Steam sales and Humble Bundles. The data was compiled using some PHP/MySQL coding, an Amazon EC2 server, and public Steam profiles. The top two most owned games were the free to play Valve titles Dota 2 and Team Fortress 2 with 25.93 million and 20.30 million users, respectively. For more on the study follow the link below.
Source: Ars Technica