If you ahve ever played the Master of Orion Series, and like the rest of us hated the 3rd game. This is for you. It really does seem like the spiritual successor to MoO2.
The second Gal-Civ has a host of new features, the AI in this game is quite simply stunning, it puts other turn based games like Civ4 to shame, it will really challenge you at the harder levels, and the suprising point is that it doesnt cheat in able to beat you. Apparently the AI learns your tactics, and every game you play the tactics you used are sent via the net to Stardock who add your tactics to a DB of known "Human" strategies, and this will be added in other patches to make the AI tougher should you prefer.
The graphics are similar to the origanal, but now has updated 3d models and is now zoomable. Combat is much improved, loading up a seperate 3d part of the game, where you can watch your fleets fight it out.
The Campaign is a lot of fun, and pretty tough.
The game has a lot of replayablility, with an online scoreboard you can submit your games to to rank against the other 100k people on the board, millions of settings 10+ races, and you can even set your own races.
You can assign your races bonuses, such as +20% morale, or +10% attack etc, there are about 40 of theses bonuses, and you get about 5 points to assign to them, so choose carefully.
Overall this is the best Turnbased game i have played yet, and without a doubt the most impressive one in terms of the AI.