Finish XCOM: Enemy Unknown

Earth lost; run a resistance from a flying base with timed missions.

Three named alien hunters who remember your fights, plus three resistance factions to answer them.

Base building, research and squads that die in the dark; the 1994 original of the tactics genre.

The underwater sequel, harder than the original in every way.

One city, two alien factions and a real-time mode; the last X-COM the original team made.

The Alpha Centauri idea again: colonise an alien planet, then choose whether to stay human.

The crew of the Unity land on Chiron and split into seven ideologies; the best writing in any strategy game.

From a settler to Alpha Centauri, one more turn at a time; Sid Meier's masterpiece of 1996.