There's Freeciv [1] for IV, and Unciv [2] for V. I doesn't have many fans, VI is too recent, and VII, well... Let's not talk about VII.
> Civ fans tend to prefer [...]
I'd say, each entry in the series gets love. The saying goes: "Your favorite Civ game is the first one you ever played". In my experience, that's pretty true (Still stuck on V).
I think the first Civ I played WAS III (maybe II at a friend's house once before?) and it ain't my fav. It sits below IV and V and even VI and I don't really like VI all that much either...
Yeah as a Civilization: Call to Power fan I have to say the “first game in the series I tried” affinity bonus is overwhelming.
Alpha Centauri was objectively the best though.