Improves on a less than great game
I'm going to be completely honest here, I am not the biggest fan of Civilization V. I feel that they oversimplified a lot of it, and took out features that really had no need to be taken out. It didn't feel complete to me, and leaving out big civilizations such as the Mongols and the Spaniards just felt wrong to me when I first played it. Granted, they did ultimately release both as DLC, the Mongols for free even, but it still felt like it was incomplete.
When I heard of what the first expansion pack would contain, I had mixed reactions. I have been saying since Civ V's release that they would be riding the expansion and DLC train with all the features that should have been in the base game to begin with, and sure enough that's what they did for the first expansion. However, what they did with the concepts that were re-used from previous Civ games have been altered in a way that makes them so much better than they were before.
First, we'll start with the main things added to Gods and Kings, Religion and Espionage. Religion in Civ IV felt like it had potential, but was very poorly executed. Other than a menial culture boost, you had no incentive to found a religion, and ultimately you just tried to get the religion that the leaders like Montezuma or Shaka had, so you didn't get your ass handed to you on a shiny silver platter. I didn't get that feel at all from Gods and Kings. First of all, there's a new "currency" to spend solely on religious means, called faith, you use the faith to, once you've founded a religion, buy missionaries, inquisitors, and religious buildings. The ways you obtain faith include building shrines in your cities and befriending new Religious City-States. Once you get enough faith you found a pantheon, which grants you a bonus, such as the "Goddess of the Festival" giving you bonus faith and culture from Wine and Incense. Eventually you accumulate enough faith to make a Great Prophet appear, who can found a major religion, giving you two extra bonuses. These bonuses are the major benefit to the religions, and can really help you out in tight spots, such as lifting your Empire's pitiful happiness rating so your empire can grow. The religions you can found include Judaism, Christianity, Islam, Buddhism, Hinduism, and even less major religions such as Sikhism, Shinto, or Zoroastrianism. Even though you can choose one of these pre-existing religions, you can also customize the name, so really, you can be the great Attila the Hun, spreading Pastafarianism across the land through brutal conquest. Really the religion is far improved upon the lackluster system in IV, and if leaving it out of the vanilla game to perfect this system was the reason, then so be it.
Espionage is also improved upon from IV, where instead of having physical Spy units, it's all done through menus, which means instead of brushing it aside as a useless feature like I did in IV, I have no reason not to use it, and it's not that bad. At the start of the Renaissance era, you obtain your first spy, and you can send him on missions to foreign cities, and you'll get all the details of that city once he's set up in there (which can take a few turns) giving you all the information you can have, as if you were looking at one of your own cities. Eventually, if he's stationed in a single city for long enough, he can try and steal technology. You can also set up Coups in City-states, which will rig elections in the city-states and put you in better standing with them. I like the system, and I also like where it's placed, at the beginning of the Renaissance, when the effects of your religious bonuses begin to taper off and become less meaningful. It's not the deepest and most intricate system, but it works, and works well.
Among Religion and Espionage, Gods and Kings adds many minor improvements that just makes Civ V a better game overall. For one, it's a lot harder to go all out conquest. I still remember the days when I could rule the world as the Germans with my four horsemen, but it's much different now. Cities are a lot stronger, and can do some serious damage to your units, not to mention making them actually tough to take over, instead of the complete cakewalk it was before. Add in a ranged unit garrisoned, and I've had units taken out in a turn. This actually makes me put a much bigger emphasis on ranged units such as Archers, the new Composite Bowmen, which bridge the large gap between Archers and Crossbowmen, and the aforementioned Crossbowmen, as well as the siege equipment like Cannons and Trebuchets, which I always realized the greatness of, but never the necessity until now. There are also new City-State types, the aforementioned Religious, as well as Mercantile, which increase your happiness with resources only they have, like Jewelry. They also made City-State interaction much better, where in vanilla, instead of doing the missions they gave me, I just threw gold at them until they loved me. Now, there are many more ways to interact with them. The missions in vanilla were always the same things. "Kill this City-State!" which in doing so just made every other Civ hate your guts for no apparent reason. "We wanna see THIS wonder!" Which just wasn't worth your time, when you could throw 250 gold at them and get a similar bonus. Now you get many more missions, like "Whoever gets the most culture in 30 turns gets to sleep with my sister!" which adds a certain amount of competition with other civs that really wasn't there before. Of course, it still amounts to throwing massive amounts of gold at them, or if your Sweden, giving them all your Great Prophets once they become useless, which is a real cheese tactic that should be nerfed somehow. It also adds new features to diplomacy with the other civs, like establishing Embassies to allow you to establish Open Borders treaties and Defensive Pacts.
The last real important thing to mention regarding Gods and Kings are the new Civs in the game. Nine new ones were introduced, Sweden, Celtica, Maya, Carthage, Byzantium, Ethiopia, Austria, The Huns, and The Netherlands, there all welcome additions, but I have one question for Firaxis. Really? You make Theodora the leader of the Byzantines instead of Justinian? Really? I can understand Dido for Carthage rather than Hannibal, but really? Theodora? ANYWAYS, Gods and Kings is a great addition to Civ V. It makes the game a lot more fun for me to play, and it feels a lot more complete than it did before. I applaud you Firaxis, you've done well.
Also, fucking Empire of the Smokey Skies, PLAY IT. IT'S AWESOME.