Civilizednation
If you ever wondered what life would be like if you controlled the country you lived in, then you need to play Civilization IV. Civ IV (or Civ 4) puts you in control of a Civilization. The game comes with 18 Civs built right in, each with their own unique units and specialties. Civilization has unique peace/war system. Want to win the game without combat? Try a diplomatic or cultural victory. There is even a space race challenge where nations are determined to build their shuttle and reach the moon before anyone else!
Unlike previous Civ games, Civ 4 lets you choose the era you wish to play in. Don't feel like fighting with swords and axes for 2 weeks? Choose the modern era as your starting game! If you do want to live through all eras but don't want to take weeks to finish a game (yes, games can get this long!), then choose the new quick game option for speedier turns.
One of the most rewarding experiences in Civ IV, is playing a very long game starting from essentially the cave man age up to the modern era, and then building nukes. You will truly feel in control of your civ when you acquire nukes. Becareful though, as soon as you acquire nukes other civs will be quick to obtain anti-nuclear weapons tecnology such as the SDI or buildings that prevent a good percent of fallout. If you use nukes, you will also cause war weariness with rivaling civs.
I honestly have to recommend a great mod for the game called Rhyes and Fall of Civilization. The mod takes the game a leap forward to provide stunningly accurate portrayals of world history. The best part is history is in your hands. Rhyes and Fall of Civilization (or RFC) comes allready bundled with Civ 4: Beyond the Sword (BTS).
Now, lets get on to the bad side of Civ IV.
There isn't a whole lot that derails Civ, unless you are playing Civ straight out of the box on a decent computer. When Civ 4 first launched, it was extremely buggy and caused the game to crash multiple times. I highly recommend downloading the latest patch for the game after you install it.
In comparison with Civ 3, the AI has definitely improved. However there are times where it becomes obvious that the AI is no where near perfect (for instance, a certain game where Tokugawa of Japan and 30, yes, 30 caravels in one city port.). The quirks in the AI don't really mess up your game though.
Last but definitely not least, Multiplayer!
Between Civ 3 and Civ 4, Civ 4 definitely comes out on top multiplayer-wise. There are so many ways to play a multiplayer match. You can play online of course courtesy of GameSpy with a built in chatroom and match finder. You can even play in hotseat mode if you have friends over who want to experience the game with out playing in single player. There is even a email mode where you can play out a turn and email the game to a friend...allthough it would probably take ridiculously long to play this way.
In the end, Civ 4 wins. It is a great break from RTS like Age of Empires, and will definitely give you a run for you rmoney. If you buy it and become a fanatic, I highly recommend buying Civilization Chronicles, which gives you all versions of Civilization prior to Civ 4, including Civ 4 without the expansions.
A good fansite to readup on the latest Civ news would be www.civfanatics.com
If you want to control a nation from birth to fall (or win :P) , Civ 4 is for you.