. . . Civilization V. Is it weird that Civilization V is my favorite Civilization game?  I feel like I get Civilization V--or maybe that Civilization V gets me--in way that just isn't the case with any of the other Civilization games.  I'm not entirely sure what magic is at work here. Maybe I just found a set of social policies that really do it for me.  I suspect, however, that it's the global happiness mechanic. When I played Civilization IV, I never quite figured out the ideal timing for founding new cities. It was never clear to me what effects founding a new city would have on my tax receipts or the happiness of my existing cities. In Civilization V, I find that it is almost always financially rewarding to found a new city so that a quick check of the global happiness score is all I need to determine whether or not to start production on another settler. The happiness meter also tells me which wonders to prioritize.  The result is a strong, stable empire in the early game, well-developed cities in the late game, and usually--but not always--a commanding lead in technology.  I've been playing on Prince difficulty, which in another game series would probably be called Normal. I've reached the point where I almost always win, regardless of my starting situation. I would increase the difficulty, but it doesn't feel like I'm winning too easily. 
I also enjoy the one-unit-per-tile rule. I'm not going to claim that it's brilliant, but it does add a fun puzzle element to combat. I particularly like that it makes the map and terrain matter as something other than a collection of production bonuses for your cities. I have come to consider cities located on open plains as easy meat, whereas I have come to regard those located on peninsulae or, worse, next to mountains with a certain amount of dread. In the older Civilization games it really didn't matter  where a city was located as long as there was a space next to it to put a doom-stack.
This message has been brought to you by Footnotes. Footnotes, keeping John's paragraphs to a reasonable length since 2017. Ask for Footnotes in your favorite forums today!
 I haven't played Civilization VI. And if you put a gun to my head and forced me to choose between Civilization V and Alpha Centauri, I'd choose Alpha Centauri.
 At least not since Civilization II. No, not even Alpha Centauri.
 Tradition. I used to go with Honor or Liberty but Tradition seems to support my preferred style of play better.
 The happiness wonders, obviously.
 A sufficiently blobbed-up enemy  can sometimes pose a challenge in this regard.
 The Mongols. It's almost always the Mongols. I think I've developed some kind of complex about the accursed Mongols.
 My last victory was actually rather nerve racking. I was playing on a Pangaea map and had three powerful neighbors with military technology just a step below my own. And that's after the centuries-long war to exterminate the Mongol menace.
 For purposes of combat.