Reunion was a bit like imperium galactica in colony management and type of buildings.
Outpost 2 sucked because the ubiquitous timelimit prevented any relaxed development I find enjoyable in simcity etc. Outpost 1 was fun, but eventually got boring as it lacked something in a goal or storyline. (something the sequel tried to remedy with fatal cnsequences)
Startopia is great fun. Especially the biodeck I like.
It's levels have varied missions to overcome.
Sandbox play is still fun because of the many aspects and occasional event such as meteorstrike or saboteur.
Can be played very offensively with security troops and droids. Droids are great.
there are several areas of enterprise: -agriculture, industry, research, medicine, entertainment, security, trade! (always have a spacedock+storage).
Enemy nations. (mediocre)
try UFO - Afterlight.
It is the third in the UFO(X-com)-inspired aftermath-aftershock series by Cenega, focussing on a martian outpost.
It has territory grabbing (by military means), research, and a little outpost development. Interesting is the limited number of troops/inhabitants. Essentially you'll have to manage with what you start out with, so medicine is not optional. Most of the game will focus around squad combat though, as is traditional in the series.