Wow, glad to see there's a new crop of young players discovering this wonderful franchise! I was 12 when I started playing also, but you weren't even born when I started playing. lol Makes me feel old.
I prefer Civ III also, mainly because it's the one I've played the most. Civ IV I think was hurt by their graphics more than helped, as far as quality of the gameplay goes. The game runs horribly sluggish on my computer, and I'm loath to spend money to upgrade just to play a game (plus I'm cheap/broke).
That being said, I do wish that some of the expandability that is built into Civ IV were available for Civ III, such as the Python scripts for generating new maps.
I dream of a map generator for Civ III that gives you the option of creating two continents, one uninhabited and one inhabited, so that you can discover the new world and colonize, etc. etc. The Civ IV map generator has this functionality, but as far as I know the only way to do it in Civ III is through editing it manually to work that way. That kinda defeats the purpose IMO, 'cause if I edit it myself I'll know where the new world is, the fastest/easiest way to get there, where the resources/luxuries are, etc. etc. Kinda kills the mystery of exploring a new continent.