It took some time to get used to Civ IV, because they changed a lot of things. But overall, I think that most things were an improvement. Infinite city sprawl is no longer a valid strategy, because cities have maintenance costs, so you can't just plant cities everywhere and expect to do well. If you do this, you will have no money to direct to science, and your archers will be destroyed by enemy riflemen. So you have to plan your city locations better. I like this because I could never outbuild the AI. There way more government options than previous games, as there are now multiple civics categories instead of governments. They also did a good job with the addition of religions. Warlords was a good expansion pack, and Beyond The Sword comes out in July, and it sounds like it will be amazing. My only real complaints are that they switched to a right click movement system for some strange reason, they went from diamond shaped tiles to squares, and the 3D graphics are completely unnecessary to game play, the only purpose that I can see is to try to market the game to the mainstream gamer who doesn't really understand what Civ is about.
EDIT: Whoever gave this a 1, at least explain yourself for trashing a game in the best computer game series of all time.