For those who want their space 4X with a bit more on
1. genetic engineering to breed new species
2. R&D to customize every single device you put into your ships
3. uniting battles and global events in the same mode
4. possibilities for devious improvisation
and a bit less on graphics, check out Aurora. It will only cost you your sleep.
A brief summary The Dwarf Fortress of 4X games
The Wiki you'll need http://aurorawiki.pentarch.org/index.php?title=Main_Page
The Forums http://aurora2.pentarch.org/

"Minimum Resolution Required: 1280x1024"

That requirement precluded me from ever trying it [I don't have the capability of using that resolution]. Reading the forums also shows that there are some severe issues with how the game is designed, especially the installer.

I found http://sites.google.com/site/gimespace/faq to get around the resolution requirement, but I'm still leery of the installer issues.

I really like Master of Orion because it's easy to learn and hard to master.

But Aurora is like work, you have to fiddle around with spreedsheets and statistics and all kind of crap which is really no fun except you are really into it. Steep learning curve and only for true HC players.

I keep trying to play this, but it gives me strange glitches all the time (Missing DLL the first time, wouldn't let me build ships the second time) but it's a pretty crazy cool game though. Hardly a MOO replacement as MOO is more like a "game" (Easy to learn, fun to play, lots of depth) while Aurora is more like a simulation.