Three games about exploring, building, and creating quite literally Anything. However what should be our main one? I'll let you all decide this, if you want to, That way we can have some idea of what we want to do. So.

Starbound: Space Terraria

Space Engineers: Survival, Construction, Eventually Automated Shipyards (REQUIRES MORE THAN JUST FOUR PEOPLE)

Stellaris, Single-player, conquest.