Everyone's forgotten that COD had a lot of haters, 15ish years ago it was called shit, everything that was wrong with "current" gaming.
So it's ironic to see the old entries grandfathered in as classics alongside DOOM etc when the narrative at the time was COD ruined FPS and people missed stuff like DOOM.
It's never been my cup of tea personally, but I'm fine with people consider the old ones classics now, I think everyone could agree the older ones are better than the newer ones.
15 years ago the Call of Duty was
Modern Warfare 2........a widely loved Call of Duty that only really had hate because One Man Army and the 1887.
Hell I remember I had a leaked copy of the game and got one of my X360s banned because I was top 20 in the world before the release date......and yeah the servers were full well before release.
2010 was BlackOps another widely loved Call of Duty
2013 was hated because Ghosts just wasnt that good.
Unreal Tournament 3 came out in 07 and it did some ~1 million units....COD would have considered that a failure.
Unreal Tournament R was literally free.
Dooms MP died faster than TitanFalls.
So the evidence has been out there for a while that classic Arena shooters werent the business.
COD staying at the top of the most played list basically year in year out proves that.
COD really only started getting hated around WWII or the changes that Modern Warfare'19 did to the MP.
Otherwise COD has pretty much always been a generally loved title, some of Sledgehammers games have been pretty weak, but if you really think about it Sledgehammer only started leading CODs with Advanced Warfare.