I agree with whoever it was on one of the pages way back that it is greatly encouraging to see folk under the age of 12 playing Civ. All the Civs and especially CivIII Conquests are great little history lessons.
For just one example, the Age of Discovery Conquest reminded me of the importance that banking played in the growth of colonialism and when I switch to a Protestant govt as Spain suddenly my Catholic brothers in France and Portugal disliked me, reminding me of the religious tensions in Western Europe. These are all small points which remind or teach people of subtle historical dynamics which influence global politics today. If I had children I would have no problem with them playing this game (in moderation) - whereas I would have HUGE problems with my kid playing Grand Theft Auto for example or MMORPGs where they might meet some pervert and constantly live in some bizarre fantasy world.
Anyway, I am 27 - have been playing since Civ 1, on and off when friends have played. However I have only become more addicted to Civ than smoking when I purchased CivIII a few months ago and then Conquests a month ago. I tried playing some MMORPGs but got fed up of them quickly (the grind sets in fast) and they are also way too detached from reality for me to remain sane playing them.
Something else worth adding: I got back to playing Civ very intensely when I changed career and was forced to move back with my parents at the age of 26. In other words I took up Civ again at a bad time in my life. Now that I have sorted my finances out and am back on track to move out again I feel I may well drop playing Civ in favour of more real life.
Point is: I generally play Civ when I'm feeling a bit down or lost. It fills up the gap and takes my mind of things, allowing me to get that 'God feeling' the game is designed to give. Any others out there like this?