Yes and Wow has been going since 2004 and the highest number of players achieved by every other MMO is the lowest of what WOW has achieved.
If your enjoying the game please go have fun.
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Not going to argue about the accuracy of the numbers, we are talking about publicly traded companies here so if they release information they might try to sugarcoat it (best selling XXX by standard XX) but you can't lie about hard numbers themselves.
And yes, certain games have a clear established playerbase and a game like Eve Online will probably outlast WOW mostly because the people playing it will probably keep on playing the game for another decade or so.
The same with Runescape, I would not be surprised if some random Twitch streamer suddenly starts playing runescape and the game gets populaire yet regardless the surge in players will never last because that's the nature of things.
What both games have in common (and why they will outlast WoW) is that the people who are currently playing the game aren't following a hype and the developer is making enough money to keep supporting the game and bring out new content,
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People have been complaining about WoW being ruined by XYZ reason since TBC.
Every single change since the original release in 2004 has "ruined the game". Arena's ruined the game, pvp gear ruined the game, flying mounts ruined the game, smaller raids ruined the game and battlegrounds ruined the game.
Is it so hard to imagine that people just outgrew WoW? I haven't really touched WOW in years at this point (little bit early during this expansion) but that's mostly on me, the game still feels the exact same game as during WOTLK yet I can't be bothered anymore in spending my evenings raiding or do whatever to get a new items.