According to SteamSpy's 2017 data, only 100 games accounted for 50% of all the sales revenue generated by Steam. This data was presented by Sergey Galyonkin, the creator of the Steam statistics site SteamSpy, at last week's GDC.
2017 was the best year for Valve so far: Steam's share of the market grew to $4.3B, not counting in-apps and DLCs.— Steam Spy (@Steam_Spy) March 22, 2018
If you're at #GDC18, come to my talk at 4PM at 2005 West for even more numbers and graphs. pic.twitter.com/j4a15aBvpZ
Galyonkin estimated that Steam's sales peaked at about $4.3 billion for 2017. Around half of that number was generated by only 100 games according to the data. That means that about 0.5% of all games on the Steam platform generated 50% of the revenue.
The games in this top 100 list are games that you would imagine being there; PlayerUnknown's Battlegrounds, Counter Strike: Global Offensive and Grand Theft Auto 5. Some other noteworthy games in this list are Civilization VI, The Witcher 3, Rainbox Six Siege, Rocket League and Call of Duty: World War 2.
It is worth noting that these figures does not take into account DLC's sold, nor microtransactions bought within the different games. These sales figures are only for copy of games sold. That's the reason why games such as DOTA 2 does not feature within this list.
This statistic further laments the issues many indie developers are experiencing with Steam at the moment. There just seem to be too many games being released, and these are all competing for only a small part of the market available through Steam. People tend to buy into the same games each year, following trends in gaming, and not venturing out of their comfort zone to try out some interesting looking indie title.
In recent years Steam has introduced various different mechanics on publishing games on Steam. This has opened the floodgates to thousands of new games to be added to the library on a monthly basis. It is already extremely difficult for smaller titles to get noticed and be successful. With this statistic that only 50% of the total sales revenue is up for grabs for them, further diminishes possible return on investment for indie titles.