Ten great games about alien invasion

Whether battling sophisticated civilisations, avoiding anal probes or shooting up monsters in Grimsby, here are the best games where you, and only you, can save the planet

Half-Life 2

Valve's brilliant shooter dumps scientist Gordon Freeman on a dystopian Earth crushed by the evil Combine alien invasion force. The visuals are wonderful, the physics are astonishing and the Orwellian setting of City 17 provides a nightmarish backdrop to the tense story of rebellion, sacrifice and shooting stuff.