In MOO1, like in GalCiv, you conquer planets by dumping your population on them (though you didn't build transports, the people just moved through space automatically). In MOO2, you build combat transports and they automatically had four soldier units aboard, so you captured alien populations instead of wiping them out.
On the other hand, in MOO1, you didn't build Fusion Power Plant type improvements, you just built loads of factories. MOO2 has a similar system of planetary buildings to GalCiv.
Neither closely resembles GalCiv in ship combat, tech trees, or food production.
MOO2's strengths are in race design, and the interesting situation of having multiple species co-existing on your planets.
MOO1's strengths are in game balance and speed of play, and in the tech tree. It's weaknesses were in some of the AI behaviours, in its primitive graphics and poor race balance.
GalCiv is... GalCiv. I've been playing it for so long now I can no longer remember its strengths, just the annoying little weaknesses. Hey, how come the tech Galactic Domination Philosophy still doesn't do anything?