Strategy games are no longer as niche as they used to be, but they still don't command the attention of gamers at large in the same way that FPS games or other multiplayer games can. As such, there are few titans to look to as the genre's key pillars, but you can definitely point to Firaxis' Civilization, Creative Assembly's Total War, and Paradox's spread of grand strategy games as such beacons.
If you're the kind of player who enjoys a good chart, such as the ones that can be found on SteamDB, you might see Civilization VI and Total War: Warhammer II sitting pretty high up the list of most-played games on Steam (looking at current and daily peaks). But you might also be surprised to learn that, when viewed in the context series as a whole, the picture of which strategy games are more popular overall changes quite a bit.
User Beneficial_Energy829, posting on the Paradox Plaza subreddit, has pulled together some graphs that look at rolling daily peaks of players for Paradox, Civilization, and Total War titles, going back to 2013. Civilization VI may be the most popular individual strategy game, but for a while now Paradox Development Studio games appear to have been the most popular strategy games in that mix.
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