I was always partial to Stars![0] though I did enjoy MOO. It looked a lot like a Windows productivity app so I could play it with no one being the wiser. It wasn't as deep as MOO other some other games but I enjoyed it.
I remember finding the limited demo on one of those "101 games!" $1.99 CD-ROMs, and then tracked down a full version at some remote Circuit City. Still have the installer and the key, and occasionally load it up on a VM (plays fine, only needed like 32mb of RAM :P )
A great game, but another one which suffered from the burden of overwhelm in the late game stages, and was hampered by the un-expected and abrupt limitation that you could only have 255 fleets (or some such thing). I read a breakdown that the cause was due to the designers only using an 8 bit integer for the FLEET_ID, so once you had that, the game would just discard any additional fleets you made.
Ahh, nostalga.
There's dozens of us, dozens!
I had a game key for a while and then lost it. So any time I dust it off to play it's the shareware version. The shareware version has pretty high limits so you can just get to "unmanageable endgame".
One of my pet peeves, especially later in the game, is there's no way to upgrade fleets. So if you've got a long lived fleet it'll be way below your current tech level. Woe follows if you forgot it was the only defense for some far flung yet important planet.