The best one is farcry 2, I played all of them, including 6

FC5. I completed within a few hours (very minimal story to it) FC4. I didn't really like that much. It seemed a little to colourful for me and didn't really pick up the storyline to it FC3. Wasn't to bad l. Was a little longer than 5 but in all the storyline was great FC2. Amazing storyline and very well over a few months of putting into it. I was on it for 3 weeks and only completed 2% of the campaign

FC6. Is amazing abit longer than 5 and there is abit more to it than what 5 had . I'm still currently playing it with main missions and side missions. It's definitely got a long storyline to it. Farcry 6 is definitely worth buying.