If you want to get Just Cause 3 to run smoothly in high quality settings then you need more than 8Gb ram in your PC. I have 12Gb which is enough but even so I still need to be careful not to have too much stuff running in the background in order to play the game. For some reason the games official requirement is only 6Gb but many players have criticised the game for being a poor quality buggy port and adding more ram solves most of the issues. Whether this is due to bad programming or not the fact remains that you need more than 8Gb ram to get the best experience out of Just Cause 3.
This is the first game I have come across that actually needs more than 8Gb. Until fairly recently even 4Gb was enough, a legacy of the memory limitations of 32 bit Windows but just over a year ago games like Witcher 3 started demanding up to 8Gb. Now it seems even that barrier has been breached.
As for Just Cause 3 itself? Once I got it running I liked it a lot. It is very repetitive and the storyline is completely forgettable but running around blowing things up never really gets old. I found the game quite relaxing to play in the evenings for the couple of weeks it took me to capture every town on the map. The relatively easy difficulty level (which cannot be changed) might be a disappointment for some but it means you can be as creative as you like in causing destruction. Foolish attempts are never harshly punished. Just Cause 3 out does Just Cause 2 in pretty much every way with bigger guns better vehicles and a much improved grappling hook. The devs did try to ape Far Cry and populated the country with many mini missions but I ignored most of them. Enjoy the game for what it is: a riotous feast of mayhem and destruction.