Gamers used to measure the success of a game in how many copies are sold. Now it's being measured in the number of concurrent players.
The phrase "dead game" has become a bit of a meme among a certain kind of gamer. If you’re the kind of person who cares about playing the most successful and popular game on the market, you might be the kind of guy who tweets "dead game" at someone evangelizing for their own favorite.
One of the most recent targets of this kind of ire is the cooperative zombie shooter Back 4 Blood, a new game by the developers who made Left 4 Dead, another cooperative zombie shooter. It's a fun game, and it's in the top 100 of the games being currently played right now on Steam, but its Steam numbers pale in comparison to the games in the top 10, like DOTA 2 and Apex Legends, leading to rival fanbases declaring this game to be "dead."
Over the past decade, as new technology allowed video games to feature more amazing graphics but also made them much more expensive to produce, video games have begun to transition away from single-player campaigns to a "live service" model. Rather than invest time and effort in developing an incredible-looking Uncharted people play through once for 12 hours and move on, many big budget games today (like Destiny 2, for example) function as a kind of platform, which is updated frequently to keep players engaged and monetized for years without having to build an entirely new game from scratch.
One of the most successful live-service games is Fortnite, a game so popular that pop stars like Ariana Grande stage concerts inside of it. This reframing of success by game development studios—away from how many copies are sold and to how many people are currently playing a game—means that fandoms of any particular game can usually levy "dead game" at whatever game they currently dislike for whatever reason.
As some people have pointed out, determining whether or not a game is "dead" is actually more complicated than just looking at concurrents on Steam. Although Steam users seem to prefer Left 4 Dead 2, Back 4 Blood is free to play for people who subscribe to Xbox’s hugely successful Game Pass service, and those numbers aren't counted in charts of concurrent players on Steam. It's also true that in some cases, a game being "dead" can say something about the culture surrounding the game. Titanfall is now in a place where almost no one can play it because of how little support it gets from its developer. But none of that really matters. "Dead game" is just an extension of the boring fandom wars of yore.
While some online games literally require more technical support or a critical mass of players in order to function, thinking of video games as either “dead games” or not is obviously not a good way to evaluate them.
Some of the best games in the world are "dead games" because they were intended to be single-player experiences, and weren’t designed to be played and replayed. Max Payne and Max Payne 2 are still wonderful works of art despite the fact that they never show up on the Steam concurrent players charts. A game that is currently on the chart in 100th place, No Man's Sky, only became so good because the community stuck with that "dead game" rather than abandoning it. There is simply no inherent marker of quality that the number of concurrents indicates. All it says is whether or not someone is playing a game right now.
This language, put in the hands of fandom, just becomes a way to show people that your horse is the fastest one in the race. It’s the same as arbitrarily stanning a console because the corporation that made it is in competition with others, and just as silly. The deadest game imaginable would be one only you play. Do the sale charts matter if you're enjoying yourself?