Civilization IV maintains the Civilization formula while improving graphics and adding a host of gameplay tweaks.
1. Gameplay
Civilization IV does away with many of Civ3 and Civ2's weaker rules. For instance, production can no longer be switched from one project to another -- if you start building the Hanging Gardens but another Civ beats you to it, for example, you're out of luck: you get some cash to compensate you but lose all progress on your project. Similarly, culture is now more viable because it helps to produce Great leaders, who in turn can aid you by quickly producing buildings or scientific research. Diplomacy now allows rudimentary coordination between allies (as in Alpha Centauri, the player can instruct his ally to attack a particular city). Stacked movement is implemented and makes managing hordes of units much more natural; while there are still too many units running around for my tastes, they are easy to group, move, and manage. Further, upgrading units as technology progresses is simpler than ever.
The downside to this ambitious game is that the player must be equally ambitious to get the most out of it. Civilization IV will take hours upon hours to fully master. Granted, you can spend only one or two hours to get the basics and play competitively, especially on lower difficulty settings. But actually understanding what is going on is another story. In my most recent game, for instance, I fielded thousands of strategic options, lost and reclaimed my capital, launched nuclear weapons, and won by a narrow space-race victory. But what were my workers and city specialists doing? I had them automated the entire time and never even had to stop to worry about what all of the specialists in my 15+ cities were doing. What is the difference between a farm and a mine, practically? One provides food and the other generates "production hammers," but what that translates into in terms of practical gameplay, I have no clue. Fortunately the game allowed me to automate this confusing procedure. (Even if I did understand it, the sheer amount of micromanagement would be overwhelming)
Fortunately, beginners will be helped out at every turn here. Each improvement, wonder, and technology can be moused over to describe its benefits, where it takes you, what units it will allow you to get, etc.
A recurring problem with the Civilization series is back here, however. The AI still cannot really decide if it is playing a game or acting realistically, as a real leader would. If it were playing to win, every country would have ganged up on me as soon as I started building a space-ship (which would soon allow me to win the game if I were allowed to launch it). Indeed, in a multiplayer game with human opponents, no one bothers to go for the space-race victory because it alienates the building player immediately. But the AI is content to play passively, and tries to win largely by building its own ship and leaving yours alone. This is in part the byproduct of weak military AI; the computer still cannot mount effective campaigns on the lower difficulty levels, so why would it want to? (The higher you go in difficulty level, the more AI units are strengthened, though, so this weakness is countered, albeit somewhat cheaply).
I'd like to see some fundamental concepts - such as the city, or the way armies are handled, or the simplistic diplomacy and economics model, changed, though. They've been around since Civ2 and should be revamped. Instead the improvements here are more evolutionary, so while the game is still superb for newcomers, returning fans might want a little bit more novelty. Hardcore players, however, will probably relish the new ruleset changes and subtle gameplay tweaks. 9/10
2. Graphics
Love it or hate it. I think they are serviceable and classy and tell you a LOT of detail at a glance. Nice, streamlined interface. Ran well on my IBM Thinkpad 2Ghz Pentium M with 512 MB Ram and a 64 mb video card. My desktop (2.8 GHz P4 with Geforce 5200 and 1 GB of RAM) could not play it well however. Strange, and I don't think turn-based games should be so demanding. 9/10
3. Sound
Leonard Nemoy reads nice, sometimes humorous quotes as the player discovers technology. Sounds and civilization-appropriate songs add some ambience. The fighting effects are also okay. 8/10
4. Value
For $40 you are getting a game that you will return to time and time again. It will take weeks to learn and months to learn well. You can, at any time, learn more about the historical background of every Wonder and improvement you can build via the built-in Civilopedia. Games can take 12 hours but, in a testament to the time-tested Civilization gameplay, you probably won't care.
Also, the amazing Civ online community is a great place to read strategies, shoot the breeze or find support if you run into problems. Visit www.apolyton.net/forums or www.civfanatics.com to take part in some of the two best fan sites I know of. 10/10
5. Tilt
I'm a little disappointed that major changes aren't here, but this is an improvement from Civilization III. Cavalry are no longer dominate; no one strategic resource is key; the game is easy on the eyes; great people and religion and the new civic system add more options. Although the game adds tons of new (and confusing) worker improvements, the automation allows the player to bypass that, at least initially. One of the main reasons I enjoy Civilization is that it gets me thinking about strategies even when I'm not playing -- should I try to convert the Romans to Judaism? Is it worth adopting a state religion to gain an ally to the north but cause a war with a neighbor to the east? You'll feel like a world leader making tough, controversial, dangerous, but ultimately rewarding calls. 10/10
** I recommend playing on a Huge earth map. Be sure to download the 1.61 patch.
Overall, Civ4 is a great improvement to the genre and the series. If this is your first Civ game, buy it now! On its own this is probably the best strategy game ever made. Those judging Civ 4 in terms of its pedesessors might have wanted a few more major changes but will undoubtedtly find the overall package extremely appealing, rewarding, and downright enjoyable.
A definite must-buy.