I sunk sooooo many hours into MOO and MOO2, especially MOO2. Then MOO3 comes along and ear fucks their formula.
It was fun figuring out how to break the game. You play through the game dozens of times with each race - if you like to risk the long game by going tech pick the Psilons, if you want to go with a shit universe go for the Silicoids, small planets Klackons (subterranean, double population), Trilarians for ocean worlds, if you want espionage go Darlocks, military go Elerians or several of the others, shit Elerians were OP in general being able to see the whole map with Omniscience, Humans if you want trading/democracy bullshit even though most races wanted to murder your children and eat your wife. Etc, etc, etc, etc.
Then you would spend time figuring out how to make optimum custom races and just straight dominate Impossible mode. I found Lithovore to be one of the most powerful skills. Zero food requirement removes your need for sacrificing population for food growth, turns building food buildings, turns wasted on food related science. I also made a beastly +Production/+Population build, but found it had limitations like India in Civ 5 (food limitations, moral issues).
The only game that has ever come close to replicating the level of enjoyment is Endless Space. My Steam library is littered with try-hard games that were either helplessly broken, buggy, or the interface was a shit-show, or they didn't allow multiplayer/co-op. AI War: Fleet Command, Legends of Pegasus, Sins of a Solar Empire, StarDrive... ugh, just to name a few.
3D fleet battles... whoopty fucking doo. I'll probably play with that shit on auto primarily anyway. I just hope they fix the GNN robot and tutorial voice-overs, because just listening to them in the 15 minute preview felt like they were jabbing spikes into my ears again.