If you like turn-based games, play it. It’s one of the best. Everyone says V is the high water mark. I didn’t pick it up until VI, but really liked it.
I have all of them. I agree that V: Brave New World is the high water mark. I play IV: Beyond The Sword on lower spec laptops that can't handle the graphics in V.
I'd vote for 6. 4 is the other "local maxima"; IMO 6 is a strict improvement on 5. They essentially just matured all of the mechanics, and then have added some new ones that aren't quite there yet (civ 7 some day...)
(Although I do miss single-city runs as Venice in 5...)
It's incredible, especially if you have a bit of time to put into it. I'd recommend Civ IV or Civ V with all of the expansion packs.