Words can't describe it, but perhaps numbers can. 9,0 (superb) rating @ Gamespot (agains't the 8,3 rating of EaW, game in the same style).
Sequel to stardock's hit Galactic Civilizations (2003), this game is simply outstanding, where you, as a player, is treated as an king, from the installation (where you're given the choice to use, or not the serial number) to the gameplay itself (where you can customize everything from the interface layout, to the ship models in an very intuitive and fun assembling tool. Robot Arena, and Robot Arena 2 players will feel very confortable with it)
Some people, like myself, say that this game is the true sequel to Masters of Orion II (wich had an frustrated official sequel in MoO 3, wich i also own. good game, but not as good as the original). There's an campaing option, where you're given choice of controlling 9 pre-set races, or you can create your own, where, with help of Photoshop, you can create your own mugshot and flag.
After selecting your race, you're set free in an galaxy (customizable too) where you need to do the 4X gameplay (eXplore, eXpand, eXploit, eXterminate).
Different from the other 4X games (like the recent Civilizations IV), there are other ways to win the game other than annihilating everyone. You can research the ultimate technology and transcend mortality, you can make an alliance with all the major races (that depends on how many races you enable to play with you, min 1, and max 9) or becoming the most influent power in the galaxy.
Wich brings to the unique feature of this game, an super-duper-ultra intelligent AI, that is more intelligent than most gamers out there. It doesn't play by cheating like other games' AI does (like limiting you to have only 50 units, while the computer has over 300 units at it's side). This one actually treats you (the human player), like it treats the other computer players (The game actually plays with itself).
At higher levels of difficulty, the AI can not only humiliate you in your own terms, but also can defeat you in ways that you will admire and respect.
For example, if you make a treaty with another race at the Beginner level, and start to surround it's space with war ships, the AI will not take that as an hostile action, and continue treating you as his friends. But at the Crippling to Masoquist level (yes, those are the names :P), the AI will see your strategical maneuver at treat it as an act of treason.
Another example is, that if you're beating down an enemy, and you come to the point of almost annihilating it, the enemy race will surrender to your rival in exchange of protection.
The graphics of the game are simply outstanding for an 4X game. Light and shader effects play very smooth even at the most lower specs. And in bug terms, the game is just perfect, not only an single bug report since the date of it's release (march 27).
Now this is an amateur review, if you want an full list of everything in this game, you should read Gamespot or IGN's review.
No matter how, buying or downloading, everyone with a taste to sci-fi strategy games must play this one!