Civilization IV brings new aesthetic and strategic elements to world domination, without losing any of the elements that made the Civilization series such a successful franchise. Graphical enhancements are significant; everything is now in 3-D (a screenshot is located here), and you now have the ability to zoom in and out huge distances - giving global navigation a "Google Earth" feel (Click here to view another screenshot).
The strategic enhancements are enormous, with the addition of 25 different civic manipulations, allowing you to tailor your civilisation in areas of state religion, government, legal, labour and economy.
Religion plays an enormous role in the social engineering of a civilisation, and you can incorporate it into your own strategic plans, with seven religions to inspire your populace and convert your neighbours. Great prophets are a by-product of your religious activities, and they, like other great people (engineers, artists, etc) can be used for discovering technology, building wonders or bringing about a golden age.
The civilisations playable now number 18 and the victory conditions have also been increased to include a diplomatic victory, that is won through passing major resolutions through the UN (just like real life, this proves to be somewhat harder than winning the space race).
Enemy civilisations have improved AI, making them behave in a more human-like way. This makes all of your decisions count a lot in foreign relations, which will affect outcomes for UN votes, military alliances and economic pacts.
More units have been added to the fray, and each unit has its own customisable promotion path of up to five levels. This is a new level of micro management for Civilization which can be automated if you prefer to focus on other things. In fact, everything in Civilization is customisable to allow you to play it exactly how you want it. Even balancing how powerful cultural and military forces are, can be changed. However, these kinds of balance customisations are left for the more advanced gamer.
The multiplayer aspect allows for an array of different playing options, the best utilising simultaneous turns and a clock timer. This allows for an almost real-time strategy feel, with the most impressive part being that players can drop in and out of a game seamlessly with the AI taking the reigns when needed.
Civ IV has also been designed for easy modification, so the game life - while incredibly long (there are still people playing Civ II) - will most likely span quite some time, since you get a user-friendly map editor with XML and Python support along with the game.
In fact, the only thing Civ IV is missing is the palace-building part of the first title, making it almost impossible to find fault with. When you consider how many hours you'll find yourself playing it, $89 is a small price to pay for such a good game.
Visuals: Great step up to 3-D with fantastic unit detail.
Audio: Leonard Nimoy does vocals, need I say more?
Gameplay: As addictive as always, you may want to book some time off work in advance.