>master of orion games (1 and 3
I've only played 1 personally, and while it's a good game with some pretty interesting mechanics, it lacks a lot of modern features and has some questionable design choices- the council, for one. It feels more like a game you'd play for an hour before work rather than a true 4x autismfest.
>Galactic civilisations
I'm not a fan of most civ games period, so this might be biased, but I found it particularly- not dumbed down- but dull. It has metaphorical rounded edges, if you get what I'm saying. You'll get the same general experience out of Civ 4.
>Alpha centauri
Yes, would recommend. Unlike 4, 5, 6 or Galactic Civilizations, it actually has scope and substance to it.
>Any other suggestions
Distant Worlds. Sins of a Solar Empire if you're more into the combat side of things.
As a side note, would especially recommend you stay away from Aurora 4x at least until it gets its C# update. Although the game superficially seems complicated, it's really, really not, and in some aspects it's far shallower than many other games in the genre.