Well, I was writing a TV show for XCOM. The gimmick being that early on there are almost no aliens. XCOM mostly fights guerrillas, terrorists, the mafia and the regular military who are all fighting over scavenging alien tech from the alien's scouting force. Nobody thinks the aliens are a threat except XCOM so everyone fights everyone. Eventually a group of civilians given psionic powers escape the alien's ship and they become their own faction as everyone tries to hunt them down and they avoid capture.
Australia is lost to the the madness (the XCOM forces fail to stop a terror mission) and the psionic civilians hide in Australia so the XCOM team follows them there.
As time goes on more aliens show up and most of the non XCOM forces realize they need to work together and people who were originally villains are now working with XCOM..... until the villains get mind controlled and become bad guys again.
And I thought I was being all original and stuff.
Anyway:
this was a really awesome trailer and really makes me pumped for the new game. Interestingly it looks like there is base defense in this game, but with a new twist.