Which ArmA is better 1st, 2nd or 3rd part?

2nd with all extras

I liked both 2 and 3, I replayed the second one for the second time, and I also play ARMA 3, there are sooo many home-made campaigns they do (About Chechnya, Syria, Dagestan, Ukraine, etc., etc....)

The question is not correct. The one with the best mission for you is better. They don't play the version of the game. but on a mission, right?
For me, this is Arma-1 with a modified Xeno Domination. There is nothing like this in A-2 or A-3 and there is nothing close by. And this is not just my personal opinion. DayZ in A-2 is quite good, but it also needs to be finalized.