Play time

This is all a long-winded way of saying that looking at the total number of players is very different from (and in some ways more accurate than) looking at the total number of owners a game has achieved on Steam, as you can see in the above chart. Games like Dota 2 and Team Fortress 2 are ridiculously popular by either metric, but looking at players instead of owners replaces heavily ignored games like Ricochet and Deathmatch Classic with popular-with-players titles like Alien Swarm and Terraria in our Top 20.

But simply counting the number of players doesn’t tell the whole story of a game’s popularity. Some games are the kinds that players come back to for months or years, sinking in hundreds of hours of play. Others are the kinds that players will try for an hour or two before giving up or blaze through in a few hours without ever returning. With Steam’s gameplay reporting statistics, we can also account for this by estimating the total number of hours each game has received across all Steam users, as shown above. (These numbers are generated by taking the estimated number of players and multiplying by the average number of hours for each player in the sample, which may introduce a bit more error than the more direct measures of owners/players).

This ranking pushes some games much higher up the list than looking at the number of distinct players alone. Empire: Total War, for instance, is the 30th most popular Steam game measured by number of players, but it's the 12th most popular game by total number of hours put in, showing just how devoted its fans really are.

Say what you will about the Football Manager games, but it's not a series that seems to accommodate many casual fans...

Other games may not be best-sellers, by Steam standards, but make up for it with an extremely devoted fan base. These are the games that everyone seems to get addicted to as soon as they play them, resulting in extremely high mean and median hours played among all owners (games with fewer than 50,000 total sales have been omitted in this analysis to avoid skewing the results with games that don't have a critical mass of players in our sample).

By these metrics, Football Manager 2014 is clearly the most popular game on Steam, nearly doubling the median hours spent of the second game on the list. Assassin’s Creed 4: Black Flag shows surprising longevity among players, half of whom put 36 hours or more into a game that reviews say only requires 20 hours or so to complete the main story. Games like Mount & Blade: Warband and Europa Universalis IV also distinguish themselves with fanbases whose average play time outperforms their raw sales numbers.

We can also use our dataset to show just how much multiplayer dominates the playtime conversation for some first-person shooters. Steam separates the single-player and multi-player versions of Modern Warfare 2, Modern Warfare 3, and Black Ops into two distinct “apps,” letting us see just how much time is spent on each (it appears "Zombies mode" play counts toward the single player numbers). While the single-player versions have the slight edge in the total number of players, the multiplayer versions are orders of magnitude more popular when it comes to average play time, as you can see in the charts above. That’s not a shocking result, but it definitely shows which gameplay mode is driving the popularity for these shooters.

The Long Tail

If there's one big takeaway from looking at the entirety of our Steam sales and player data, it's that a few huge ultra-hits are driving the majority of Steam usage. The vast majority of titles form a "long tail" of relative crumbs. Out of about 2,750 titles we've tracked using our sampling method, the top 110 sellers represent about half of the individual games registered to Steam accounts. That's about four percent of the distinct titles, each of which has sold 1.38 million copies or more. This represents about 50 percent of the registered sales on the service.

By contrast, the bottom 1,000 games, which have sold less than 30,000 copies each, represent just 1.6 percent of all the registered games on Steam, forming a relatively paltry "long tail" of sales for relative underperformers. The median game on Steam sells just under 50,000 copies on the service, according to our estimates, while a game in the 25th percentile has sold about 215,000 copies. The distribution looks pretty much the same when looking at the number of players rather than the number of owners.

Things look even more dependent on a few big games when you look at data on actual gameplay. As shown in the chart above, about half of the estimated 18.5 billion man-hours that have been spent across all Steam games have gone toward just the six most popular titles. Dota 2 alone makes up a staggering 20.7 percent of all Steam play time, reflecting the free-to-play game's dominance both in terms of sheer numbers of players and those players all pouring countless hours into the game on average.

This kind of distribution isn't all that surprising when you think about it. Video games, like most forms of entertainment, are a hit-driven business, a few works becoming mega-popular and the vast majority struggling to attain any significant traction at all. This kind of long tail, hockey stick shaped popularity graph has been applied to everything from weblog rankings to ad spending in recent years.

Still, it's striking to see just how hit-driven the market for Steam games really is. The service slightly outpaces the well-known 20-80 percent rule of the Pareto Principle, with the top 20 percent of individual titles representing about 83.1 percent of all sales and 87.7 percent of all played games by our estimates. By total hours played, the Principle goes flying out the window, with the top 20 percent of games representing a full 98 percent of total play time.

To make a long story extremely short, there's a reason why publishers chase those rare big hits—because the top few relative performers make up an outsized proportion of the sales and usage data on a service like Steam. When it comes to finding success in PC gaming, our data shows there's a huge gap between those top performers and the thousands of also-rans that make up the bottom rungs.

[Update: Since this story was published, we've addressed some concerns with our data and methodology in this update]