Possibly the best space strategy game ever made
The unique element that stands out the most for me is the ability to design your own ships, it can be very addicting and time consuming, it's somewhat like playing with legos, there are tons of parts that can be connected in anyway you like, only your imagination is the limit.
Another element concerns the atmosphere of the game, GalCiv2 takes a bit different approach to the genre by adding some humour to the mix. It was a good move by Stardock as it lightens the game's atmosphere significantly and makes it less dreary.
The third feature you don't often see in strategy games is the choice between good and evil, every now and then you are presented with interesting choices concerning your citizens which will affect your alignment which in response will affect how other races perceive you, there are also some different "bonuses" once you finally commit to the path of good, evil or neutral.
Other than those 3 elements it plays out much like your standard TBS/4X game with a lean interface, good AI and well balanced gameplay. There is a campaign in the game in which you play as humans and fight the Dread Lords, a powerful and ancient race that has technological upper hand during the whole scenario. It's no epic tale thanks to the meagre presentation, but the intentionally unbalanced sides do add certain flavour to it and it's worth playing. But personally I've always thought that the custom games are what make or break this type of games.
There are several alien races you can play as or against, as well as create your own custom race. In the custom games you start off with a single planet, a flagship for exploring and a colony ship to populate a single uninhabitet planet. It kicks off the first part of the game which consists of exploring and expanding. Bying and building new colony ships and finding new habitable planets at a rapid rate is essential for the rest of the game.
You could say the game is divided into 5 categories - Research, Economy, Culture, Diplomacy and Military. Naturally you are unlikely to make it simply by concentrating in one area. Massive army costs massive amounts of money and so on, you need a balance. But you can specialize in any of the areas if you wish.
Research tree is impressive, there are lot of different paths to take and special technologies to achieve. Economy is quite simple which I was glad of, you can control taxes, build banks, freighters and starbases etc. There are lot of options but it's never overwhelming.
The diplomacy in the game is splendid, pretty much everything can be traded from individual ships to influence points, but once again everything is presented neatly on a single screen. Your diplomacy skills will affect how they will receive your propositions, as will your trade relations and other factors. There is also a sort of Galactic UN where you make choices concerning all races, the votes are called influence points and are related to your power and culture.
The AI is one of the best I've seen, it never seems to cheat but always provides a challenge, which is good since there is no multiplayer. Making allies is quite important, because the other races certainly do make them and you don't want to be left alone against a coalition of races surrounding you. The minor races that might appear during the game will add their own color to the galactic events too. All in all the AI is suberb, allies are useful and enemies are dangerous.
After you've explored, expanded and exploited your neighbours enough comes the time for the 4th X, which is eXtermination. There are lot of things to consider in a fight, there are 3 main types of weapons, mass drivers, missiles and energy weapons. Each of them have huge number of different variations that need to be researched separately, and each type of weapon has different defences to counter them. Armor, shields and point defences. It's sort of a rock paper scissors type of ordeal which means you need to plan your moves ahead, converting to another technology on the fly isn't easy.
The great thing is that you can, and should, design and build your own ships making each fight and playthrough a bit different. One of the major things to consider is the hull size, it's not always so apparent that bigger is better. Colossal starships may travel faster and survive several battles, but are slow to build and expensive to maintain. Small fighters can be build in few turns across several planets and gathered together in effective fleets eliminating the need for large reserves.
Of course after the enemy is defeated in space you need to take over their planets as well. You can make the invasion a bit easier by nudging few asteroids towards their planet or perhaps you'd rather soften them up with chemical weapons. The battles themselves are fought automatically, it's as simple as moving your unit on to another. But there is a 3D view for space battles and they can be entertaining enough to watch when sped up.
There is great amount of depth in GalCiv2, yet it's presented so that it doesn't feel intimidating or overwhelming. It retains the addictive nature of turn-based strategy games and I certainly recommend the game to anyone who likes them. To those that don't this should be a great introduction to the genre.