I honestly don't recall how long I've been playing some version of Freeciv; our last home computer ran version 1.10 almost until the day it died, despite being a Linux machine and not exactly cutting-edge even when we bought it. While other boys my age were getting sunshine and exercise, I was learning the importance of Michelangelo's Chapel and Cruisers. Eventually, I even figured out how to edit the rulesets of the game to create new nations and units--one of the few advantages of Linux.
Newer versions rendered this unnecessary, as they added far more countries than I would have thought of on my own. By the time I was clandestinely installing version 1.14 on my high school's computers, it was possible to play civilizations as outlandish as the Filipinos or the Cornish. Now with the installation of version 2.2 I can play anyone from the Ainu to the Westphalians if I so choose.
Alas, the AI still leaves something to be desired, although with 2.2 the computer seems to have acquired a certain degree of cunning--enough to contest some of the wonders, but not usually enough to be a threat in the endgame. Fortunately, there is a multiplayer option, and from time to time my brother and I have contended with each other. Still, for whiling away the hours, the AI provides at least some sort of opposition. And there's something satisfying about building one's chosen people up from a tiny little two-city country to a mighty industrial empire that spans continents and sends expeditions to Alpha Centauri.
(Oh, and bonus points for anyone who recognizes the nation in that second screenshot without resorting to Google. Apparently the Himyar were a tribe in pre-Islamic Yemen, but more importantly they have a neat-looking flag...)