Space Empires IV Gold is one the best games I have ever played.
Space Empires IV Gold is a turn based game in which you create and manage a galactic empire. It gives you the options of micro managing ever aspect of your empire including space ship design, diplomatic relations, research and development, and turn by turn ship movement; or it allows you to some or all of those functions over to AI ministers.
The game can be played in a quick start mode with pre-made races or you can build the game from the ground up including the creating of races, galaxy maps, tech levels, etc. It also has a PBEM mode and a play over IP mode.
It is also fully mod able and the CD that the game comes on has numerous mods you can install and a guide to modding the game.
Downsides: It takes a while to learn the game, but it does come with a very good tutorial. And the tactical ship combat leaves a bit to desired, but you don't have to use it. The multi-player modes take a bit to set up, but play very well once they are setup. And the price is a bit high, but I figure that is because of lack of demand and exposure.
So if you like epic scale galactic empire games, check it out. It is all it is cracked up to be and more.