Despite the massive library of games available on the Steam marketplace, and the popularity of Steam sales, Valve's own free-to-play titles Team Fortress 2 and Dota 2 dominate the service.
Dota 2 alone has an estimated 25.9 million players, with a total play time of over 3,800 million hours, according to research published by Ars Technica today. Team Fortress 2 has a comparable 20.3 million players, but less than half the played hours, at just over 1,400 million. However, that's still more than twice the amount of hours put into mega-hit The Elder Scrolls V: Skyrim.
The top six most played games, of which four are Valve titles, together account for almost half of all play time on Steam. In perhaps the most impressive finding, Dota 2 alone accounts for over 20 per cent.
The stats also reveal the large 'backlogs' of unplayed games owned by Steam users. An estimated 36.9 per cent of owned games are never played, and a further 17 per cent are played for less than an hour. This is likely a result of Steam sales, which see games regularly sold at substantial discounts.
Last month, Kotaku reported that, of the gamers surveyed, the average person bought 60 per cent of their games on sale, and that out of 11 to 25 games purchased in the last year 40 per cent would not yet have been played. It also found that nearly a third of gamers have over 50 games in their Steam library that they are yet to play.
In March, Positech Games' Chris Harris aired his misgivings about this culture of extreme discounting. In a personal blog post, he claimed that "the endorphin rush is now from getting a bargain, not the fun of actually playing the game".
He also suggested that this "devalues" games, preventing proper player investment and leading to games being discarded at the first sign of confusion or difficulty. Given the overwhelming popular time investment in the free and highly complex Dota 2, however, the truth seems far more nuanced.
What is clear is that the free-to-play business model is more important to the PC gaming market than ever before.