Ascendancy

The Good
There are lots of space conquest sims on the market, but "Ascendancy" is the most different of the bunch.

It's not much different from most space conquest sims except that this game offers REALLY different races; as opposed to just "this race gets a slight defense bonus, this race gets a slight ground combat bonus," Ascendancy races play very differently and, (the coolest thing about the game), have victory conditions for each race that don't involve conquest. For one race, you win if you can convince everyone to be at peace with everyone else!

The Bad
Planet management is very, very repetitive and boring. It's good stuff but there's just too much repetition.

The game's major drawback, though, is the astoundingly bad AI. Enemies are mind-bogglingly dumb and overly easy to defeat.

The Bottom Line
I know it's bad English, but this is the most unique take on the genre I've ever seen. Worth playing.