This game, distributed by Microprose, had two names. I think it was first released as UFO: Enemy Unknown, then X-Com: UFO Defence. In X-Com, you command the secret internationally funded X-Com organisation. The X-Com organisation is a mix of scientists and soldiers. Soldiers fight with the aliens to protect helpless citizens of earth (and their cattle) and capture alien life forms and alien technology from these encounters. After returning from a successful mission, the loot is researched by the science team. As the database on the aliens grows, their master plan (and X-Com's counter) can be determined.

The game consisted of various styles of gameplay, the major style being an isometrical turn based squad-combat scenario. Extremely addictive & creepy. It was followed up by three more games.

Two more games set in the X-Com universe are being developed right now. One is a first person shooter based on the Unreal Tournament engine called X-Com: Alliance. X-com: Alliance seeks to incorporate the acquisition and research of alien artifacts/bodies that all the X-Com titles have had. The plot involes an X-Com squad stranded on an alien world (I think).

The second looks like it has the ability to raise X-Com back to its original status. X-Com: Genesis is aiming to be more like X-Com: UFO Defence/UFO: Enemy Unknown than any of the other titles. None of the other games had the feel of the original title. It looks like the developers have realised this, along with the mistakes of unabandoned genre jumping.