I played MOO then MOOII a lot but finally found it too easy even on impossible. Also I got tired of the AI cheating so much. Tactical combat was great, especially ship initiative. I used the race pick that got all the techs in an area researched, heavy gravity, and subterranean. I really hated the Saccra, seems like they bred like flies and were usually the race that gave me the most problems. But I guess this is not the right forum to talk about MOO. It is dead and gone so far as I am concerned. SE IV is the game of my dreams!
You forgot to mention Ascendacy - it was ok for a few months play.
Although not a SPACE empire game, the Civilization series was pretty good too. In all I got a couple years play out of that.