I see Far Cry games are on sale - I've never played these games. Is the first game a good place to start? That's kind of what I'm thinking.
Far Cry 1 and 2 are pretty different games. FC1 doesn't age as well as FC2 does. But FC2 is definitely interesting enough to warrant at least a cursory glance. FC3 is a good mix of modern shooter design and kind of the start of the Ubi open world formula they've come to be known for. FC3 is probably a great starting point, but honestly, just pick the one that has the most interesting setting to you, they aren't connected in any ways that matter or make a difference. They are all pretty self-contained.
Of the Far Cry games I've played 2, 3,
Blood Dragon, Primal are all pretty fun if you don't have a buddy to play with. But if co-op is a possibility, FC 4 and FC 5 are really good times with friends. Very very fun.
Didn't spend much time with FC6, but it more or less felt like different flavors of the same FC4/5 formula. But really, the first 5 or so FC games offer some pretty wild rides and as long as you aren't the type that categorizes things into "best or worst"; the franchise has a lot of fun to be had.
If you are interested more in Sci-fi in general, pick up Blood Dragon, it's the best 80's nostalgia tribute you could get with the formula. Great time. Or pick up Avatar: Frontiers of Pandora, it's essentially sci-fi Far Cry with co-op.