I'm new to civ iii, and i've found that some hall of fame games took around 50 hours to complete a domination victory. I don;t want to play games that long.
It is just an issue of mind over matter.
If you don't mind, it don't matter.
(Okay, that is trite and simple, but it is true.)
Let's ask the question another way:
Do you expect to get 50 hours of enjoyment from Civ III?
Well, you don't know yet, since you are checking around, but if you got the game for $20 you probably expect to enjoy it for at least 20 hours. And you've come here for advice, so you obviously don't want to play the game poorly.
It would be nice to say that a longer game is a better played game...but it is not. My first CivIII game lasted over 40 hours and I lost. Standard map size with continents. On Chieftain. As Rome.
My first HOF game (Huge, Conquest, Monarch, India) took over 200 hours. I was slow and I was logging stuff every turn, which added quite a bit of time. Did I enjoy the game? You bet. Did I begrudge the time invested? No.
I do understand that sticker shock feeling when the game tells you how long it has taken to play. I was taken aback when my first game sprang that fact on me. But don't let the fear of a big number on the ingame stopwatch stop you from having fun.
Play the game the way you want. If you don't enjoy it, it won't matter how long it took; you won't play it again.