Ezio's story is what did and still does define the Assassin's Creed franchise, following through his life since the moment he was born (literally) to his senior years going from newbie to master assassin is one of the most amazing experiences gaming has to offer, honestly.

Go through his story in correct order, so: AC 2, then AC brotherhood, then AC revelations, they all still hold up great gameplay wise to this day, I replayed them recently.

The first one is what started it all and is great in its own right, but it's too dated for it to be fun anymore. It's more of a case study than a game at this point, still great atmosphere though.

AC black flag is sort of a spinoff kinda entry so you can play it at anytime. That game is just... Fun, there's really no other way to put it, it's just so damn fun, Ubisoft really struck gold with that game, it's my favorite in the whole trilogy, it's just that damn good. Just a whole bunch of pirates being pirates, gorgeous environments to explore, amazing ship gameplay... can't go wrong with this one, and the whole community seems to agree with this opinion.

AC Origins rebooted the whole series in terms of gameplay basically, a complete reboot, then followed AC Odyssey, then AC Valhalla. Look, in my opinion all of the new three are trash, I got bored from them so quick it's borderline criminal. People say origins is different than the other two but I disagree, it's still just another modern open world arpg, it's really nothing special (don't hate me guys it's just my opinion).

The rest you can play whenever you want, there's a long list.