The biggest changes are within the game's combat system, which now disallows stacking units. In previous Civ games, combat was about throwing large stacks of units against other stacks of units, then having the math add it all up and declare the winner. It was boring and not at all representative of real military combat. Now, since only a single unit may garrison inside of a city, combat takes place around and away from them.
Speaking of cities, they can defend themselves and have their own hit points. It isn't absolutely necessary to keep a unit in them at all times, which frees up your ground forces for exploration and pillaging elsewhere. It also makes siege units, both land and sea-based, extremely important. It is so refreshing to have a navy mean something in this game as they can destroy land units and really put the hurt on cities.
Ranged units are now truly ranged units, no longer just "melee" units that counter specific types of enemy units. They are actually ranged attackers and can do so from behind your front-line forces. Army mixture is very important and leads to some exciting conflicts. It's also harder to crank out stronger units as resources are now finite.
In previous games, powerful units that required access to specific resources, like iron, were simply unlocked when your empire gained access to the mineral. You could then make an unlimited amount of these units. Now, resources are limited and you may only gain a few units of iron with each node. Each time you make a unit that requires iron, for example, your total available iron decreases. If that unit dies, you get that iron back. This helps balance the game immensely and ties into the focus on more expensive, valuable units instead of massing as many as possible.
There are many more facets to the new combat system, but all in all, the combat is extremely engaging and the thing I enjoy most about the game. It works well with the move to hexes, which allows the game to be beautifully presented, but also works well for flanking and arranging units.
On the city-building side of things, gamers are likely to find less systems at play than with previous Civilization games, but that isn't necessarily a bad thing. Religion, as its own system, is gone. Culture, while less effective at overtaking enemy territory through influence, is plugged into the game's new policy system. The policies are similar to talents that you might find in games like World of Warcraft or like perks in Fallout. They offer bonuses along certain lines of strategy. One tree might favor empires with a single city, while another might improve a rapidly expanding city. This makes culture extremely useful for boosting any other aspect of the game. Similarly, gold can be used to immediately purchase buildings or units, as well as buy new hex tiles to expand the borders of a city.
Gold can also be used as a gift to the various city-states scattered around the map. These AI-controlled city-states are limited to a single settlement and will not try to expand or attack you without provocation. If you stay in their good graces, you'll be rewarded based on the type of city-state they are. Militaristic states will give you attacking units, while economic states may provide you with gold or resources. The system has enough depth to be powerful in particular strategies, but isn't invasive enough to require any interaction at all. It's just another choice presented to the player.
Choices require information and thankfully, Civilization V presents almost everything up front. The new user-interface is clean, efficient, and reminiscent of modern operating system design. A quick glance at the top bar will tell you everything you need to know about your economy, while mousing over any particular item will give you the full breakdown. It's this information that allows you to make changes based upon the needs of your empire at any given moment. I will say that the late game tends to evolve into having less city management than military action, but that could just be my playstyle. I'll be interested to hear what more diplomatic players experience.
Gameplay Demonstration Video
The AI in the game has also undergone a major improvement, especially since Firaxis has chosen to hide the raw numbers of diplomatic relationships. In Civ IV, you would directly see the effect of different things like religion or previous military action. This was the one place I didn't want exact numbers because that isn't how people interact. I suspect much of that math is going on in Civ V, but hiding it does a lot to make the interactions between you and the soulless computer program a bit more realistic.
Each civilization only comes with a single leader and I would have preferred a few more. The bonuses and unique units of the various leaders are exciting enough to make a difference in how you play the game, but not so powerful as to unbalance the game. Multiplayer is currently limited to simultaneous turns, but games can be set aside and picked up again down the line through auto-saves. Manual saving of multiplayer games is not possible. More modes are planned following the game's release.
All in all, Civilization V is an amazing game. Firaxis has changed so many things, but manages to keep the feel of what makes this a Civilization title. There's a major level of polish across all facets of the game and it is absolutely gorgeous. It can be a bit of a resource hog as games progress, but it won't require a top of the line rig. Series veterans will find welcome changes and newcomers should enjoy learning Civ in this version.Developed by Firaxis Games and published by 2K Games, Sid Meier's Civilization V will be released for PC on September 21 in North America, then in Europe on September 24.