Is it really that good?
Also, If I have never played any CoD, how and where should I start?
If you mean singleplayer campaigns: as far back as you can stomach the graphics of.
If you actually want good campaigns, Black Ops 1 is fuckin legendary. World At War was also great. As is Modern Warfare (2007) and Modern Warfare 2(2009). Modern Warfare 3 (2011) was also good. Black Ops 2 was good. I wouldn’t bother with any further Black Ops games- one of them doesn’t even have a campaign iirc.
For the much much newer titles, Modern Warfare (2019) was good. Modern Warfare (2022) was also solid. Modern Warfare 3 is ‘last years title’ being referred to in the OP.
None of these are narrative masterpieces exactly- the closest is probably the Black Ops games. With that said, they’re very much ‘action movie’ videogames. Tons of crazy set pieces, unique segments, and then the cutscenes that usually tie together a reasonable enough plot to be interesting.
If you mean multiplayer: honestly just jump into Black Ops 6. None of the older titles are likely to be a great experience at this point. Or just spend your time on a better game lol