The above animation is perhaps the best illustration I've seen of how exactly Steam users' tastes have changed since 2015—or, more accurately, how they've stayed roughly the same. It shows the top 15 Steam games by player count for every day since January 1, 2015, and runs through four years in 50 seconds. If you have a spare five minutes, I'd recommend watching TheRankings' original video here. The gif above, from gfycat user TheKarmaFiend, is a sped-up version.
A couple of things to note: firstly, you can see just how steady both CS:GO and Dota 2 have remained. Secondly, the animation shows how meteoric the rise of PUBG was—after some slow, steady growth throughout April 2017 it just explodes, warping the scale of the graph with its huge player numbers. At one point in December 2017, it held the top spot, while its test server ranked fourth. Remarkable.
Other top 15 constants include Team Fortress 2, Warframe, GTA 5, Rocket League, ARK: Survival Evolved and Garry's Mod. It's also oddly satisfying to watch iterations of Football Manager swap out towards the end of each year: Football Manager 2018 drops off the list in October 2018 and is replaced, almost immediately, by Football Manager 2019.
Other games make more fleeting appearances. Watch closely in August 2016 and you'll see No Man's Sky catapult up to third in the list. Mere days later, it's gone again.
How did your favorite game fare over the past four years?