Unfortunately, I started at Civ V, but I like Civ IV's theme song immensely! It's the only game where I can nuke Ghandi and not feel bad about it.
When I start playing it ( which admittedly hasn't been in a long time) I usually don't stop for many hours and have games as long as 80-100 hours usually.
Yeah, these empire building games are addictive. I remember playing Star Wars: Galactic Battlegrounds until the crack of dawn without even realizing it. Not the best idea in the world when you have work in the morning.
I like Civ IV better. Just because the combat system is better than in Civ III, and um...almost everything is better than Civ V. :/ Lots of people who played Civ IV before Civ V came out feel the same way. Then, people who played Civ III before Civ IV came out feel that way about Civ IV. So yeah.