FC4 for me. Much more varied locations, you are not forced to help a specific faction and instead can choose who to help (or help nobody at all, if you choose the secret ending). Because there's multiple factions, there was actual replay value, because missions were mutually exclusive (if you did a mission for A, you can't do that mission for B, and A and B had different goals for the same mission (burn vs steal, capture vs kill)). These things were pretty unique to the series, and much more meaningful than having something as shallow as 3rd person cutscenes in FC6.

Far Cry original was almost story driven horror for most of the game, and it was CryTek, so I almost consider it a different game, much closer to Crysis than Far Cry series.

Far Cry 2 was incredibly immersive - no HUD, no minimap showing enemies around you, weapons were breaking all the time, etc. It was realistic, having to visually locate enemies lurking in the bushes, and very immersive. I'd have loved for someone to port it to VR.

Far Cry 3 updated to a different formula, but was largely derivative. Minimap, marked enemies, weapons don't break, etc. It felt dumbed down, primitive. The only nice thing about it was the tattoo-based character specialization system. It was a nice, simple formula, and decent on-the-rails story with one or two choices along the way. Fewer choices than in FC2 if I remember correctly (buddies, the ending fork choice, etc).

Far Cry 4 was an across-the-board improvement on FC3, and as far as I'm concerned that's where the series peaked. Good story, good character development, good villain, multiple factions to side with, immense replay value compared to any other game in the series because of mutually exclusive missions, etc. Just all around special.

Primal is next, and I kinda liked it. Reminded me of Apocalypto movie, with the different tribes. The perk system from FC3 was back, mostly. Weapons breaking was back from FC2. Animal companions were fine, especially the ones you could ride. The need for winter clothing to go to certain areas and moving from fire to fire so you don't freeze reminded me of the storm mode in The Division. It was fine, I enjoyed it quite a bit. But it still felt like too much of a step back from FC4.

Far Cry 5 was a curious setting and story, but the forced kidnappings and combat scaling of enemies kinda ruined it for me, combined with the mute protagonist and lack of character development. The only thing about it I liked was that you could have 2 companions, and they would talk to each other as well as you, which lead to some interesting and sometimes funny interactions. But it had a REALLY unsatisfying ending. The ending was so bad I went and got New Dawn just to wash the aftertaste of FC5 out of my mouth and get some closure, but enemy scaling was even worse, itemization was vile, campaign was short, the grind to upgrade the settlement just to be allowed to finally finish the game was absurd. The worst game in the series, New Dawn was, for me at least.

And Far Cry 6 was different day, same shit. We lost the combat companions in favour of the amigos who can't talk, so that was a massive step back to a pair of talking NPCs in FC5. Some of the disgusting RPG-like enemy scaling made its way back from New Dawn, as did haphazardly assembled "guerrilla" weapons with jury-rigged silencers that fail. Too many similarities from New Dawn, and too many steps back from FC5. Also Giancarlo Esposito was CRIMINALLY underutilized, which was just a shame. Reminded me of how Bethesda hired John Goodman for Rage, used him for a grand total of 5 mins, and you never see or hear from him again. Like...what was even the point? Just a blatant bait-and-switch.