The lights are on
Thanks to the advent of high speed internet and online gaming networks, we live in a time where our games can be enhanced by all manner of downloadable content. Rather than releasing entire new games with some combination of the words "super", "hyper", or "turbo", Capcom for example can simply release Street Fighter DLC via Xbox Live or PSN. These addons can extend a game's lifespan and fill in the time between releases; however, most ordinary DLC give precisely this impression of "game filler" rather than "game changer". Of course, Civilization is no ordinary game series, and its latest addition, Civilization 5: Gods and Kings, stays true to the series tradition of consistently stellar releases. Not simply being content with the addition of 9 new playable civs, 4 scenarios and the religion and espionage gameplay systems (among other additions), Gods and Kings turns the game upside down and propels it into a new dimension, leaving the player wondering how they ever got along without it.
Truly, the most exciting time for a game is immediately following its release: pre-release hype hasn't worn off, the servers are full (for online games), and a sense of wonder and the yearn to explore captivates every player. As time goes on however, the game's boundaries and limitations are eventually discovered: glitches exploited, optimal strategies calculated, and like a chess playing computer creativity and imagination give way to a mathematically determined "best" way to play, diversion from which nearly guarantees defeat. Gods and Kings, I am happy to say, has tackled this problem straight on, primarily through the revamped religion system which puts its Civ 4 incarnation to shame. After building your first few faith points (a new resource) you choose a cult, which brings with it a chosen benefit (such as +1 production for every 3 followers). Once you earn a Great Prophet (a new great person which randomly spawns after a given amount of faith is earned) you can found a full religion, which allows you to choose two additional benefits and purchase missionaries to spread your faith, adding further depth to diplomacy. These benefits combine to give you an unprecedented level of customization for your civ, and ensure that no two games will ever be the same. This theme of customization and creativity is reflected elsewhere in Gods and Kings: the Piety tree, essential to the cultural victory, has been transformed into a hybrid Faith/Culture tree, and in a sense "nerfed". This does not mean that the cultural victory is now more difficult; rather, it forces the player to explore alternative paths to victory rather than funneling all production into culture and praying that nobody stumbles upon them and their single city conspicuously stacked with half the world's wonders. Gods and Kings is an effort to make every game of Civ less predictable, and the revamped religion system is central to it.
An improvement touted in the Gods and Kings trailers is that the AI is now more intelligent, particularly concerning military matters - no more stray Great Generals or disorderly units. My first few rounds of the game confirmed this; thankfully, you now have new tools with which to engage your foes through the Espionage system. Starting in the Renaissance era and for each era onward you recruit a spy. These units are (appropriately) invisible on the game map and are accessed via a separate menu, which displays myriad information such as the spy roster, target cities and uncovered information. With your spies you can steal technology, rig city state elections to alter influence both for yourself and others, see what your opponents are building and discover plots being made against yourself and other players, giving you a heads up to an oncoming attack. The espionage system is an engaging addition that provides an exciting alternative to waiting around for your opponents to make their move.
Speaking of making your move, combat has also received its fair share of changes and improvements, particularly naval units. There are now two varieties of naval units, ranged and melee, as well as the Great Admiral, the naval version of the Great General. Combine this with the fact that embarked land units now stack with naval units and maintaining a competent navy has now become critical to military success. Changes to land units such as a 200% increase in artillery damage toward cities, 100 base hp for units rather than 10 and the addition of units such as the Gatling gun are all part of an effort to force the player to think strategically: simply swarming melee units will not grant you victory. The player must maintain a balanced and diversified force, and long term strategic thinking as well as short term tactical brilliance are both requisite to victory.
This expansion was two years in the making (Civ 5 being released in 2010), and the clear amount of effort put into this game reflects well upon the time spent on it. Subtle improvements such as the redivision of the tech tree into different eras, the reassigning of city states to types which reflect their historical roles (Tyre for example is now a Mercantile city state rather than a Military one), and the addition of new luxury resources give this expansion a level of uncommon polish. Combine this with 9 new playable civs with intriguing abilities such as spending gold to annex city states, moving over mountains and stealing opponent city names, and you have an expansion that is not merely additional, but essential.
In conclusion, Civilization 5: Gods and Kings is an expansion that is not satisfied with merely adding to the game: it improves upon it in every conceivable way. This is the standard to which all expansion content should aspire.
Edit: I incorrectly stated that there are 4 new scenarios. There are only 3 (haven't touched them much yet, been busy with multiplayer).