X-COM: UFO Defense (known as UFO: Enemy Unknown in Europe) is routinely named the best strategy game ever made, and nearly thirty years on, nobody has convincingly argued otherwise.

Julian and Nick Gollop's design splits the game in two: a global geoscape where you manage funding, radar coverage and aircraft, and a tactical isometric battle where your soldiers fight aliens door to door. Both halves are punishing. Both are fair.

Why it endures

The magic is in the stories the simulation writes. A rookie named after your friend panics, throws a grenade at your veteran, and levels the building you needed intact. Terror missions in port towns at night remain the tensest twenty minutes strategy gaming can offer.

The catch

The interface is a museum piece - every action costs too many clicks - and the difficulty curve is really more of a cliff. OpenXCOM, the open-source engine port, fixes most of this and is the recommended way to play in 2026.

Verdict: the benchmark against which every squad tactics game is still measured.