Sid Meier's Civilization IV can be described in the same way that people are describing
World of Warcraft. It has taken everything that was dull, boring, and frustrating with the previous games and eliminated them. The core gameplay that was left has been tweaked slightly to create as deep an experience as the prequels offered, but no less fun. This, with the addition of some new features, adds up to create one of the most compelling strategy games of all time.
Less notable of a change at first is the AI. The opponent settings still range from super easy to Deep Blue-like quality. However, the standard setting has had its cheating privileges revoked and now relies more on its artificial mind to achieve victory. Diplomatic relations have also changed. There are many ways you can win at Civilization IV, one of which is through diplomatic means. Instead of just being able to trade goods, you can now ask them for favors (like declaring war on other players) or offer to keep borders open.
Religion, though a small addition, can also be used to help garner victory. Though there is no "Religious Victory" in the game, you can influence your neighbors to change to your religion, or you can adopt theirs, improving relations greatly. The emphasis on religion is small probably because it is a new feature and the developers didn’t want it to get out of hand and imbalance the game. However, they are on a good start with it, as it adds a nice little dynamic element to every game you play.
Another new feature is the inclusion of Great People. These units go a long way towards helping you achieve a cultural victory. Depending on the structures you build and the amount of culture your cities are generating, you have a chance of creating a Great Person. There are many different kinds, and if you manage to get one, their unique abilities can be used to inject a hell of a lot of culture into your civilization, increasing your borders, influence, and production rate.
Of course, there is always the military victory. Combat has been made easier to get a grip on, as units now have a strength and defense and also gain experience. Upgrading your units is not just a matter of bumping their attack levels. Units can be upgraded to do very specific things; city attack bonuses, defense bonuses, and healing bonuses are just a few of the many abilities that your combat units can attain.
Civilization IV is turn-based, and those who have played the previous titles know how long some of the games can get. In this version, the player has more control over customizing each game to the degree of length they like. Options for quick games will allow you to complete a conquest of the world in a matter of hours, while other options will make the game take a much slower, more methodical route.
Multiplayer is as robust as ever. Up to twelve people can play in a variety of different modes. The standard turn-based game, with the turns on a timer, is the most common. There is also the mode where everybody issues their moves at the same time and the turn plays out accordingly. Those with less time on their hands can opt for the play-by-mail mode.