I've taken the liberty of writing a treatment.
Act 1: We meet our protagonist, Joe Six-Pack, who has a wife and 2.3 children and works a dead-end job. Space invaders show up and destroy a bunch of famous monuments. In the ensuing chaos, the wife is killed and the dad vows revenge on the invaders.
Act 2: For some reason, this average joe with no particular skills ends up being one of the key players in the war against the space invaders. He develops a friendly rivalry (with just a hint of homoerotic subtext) with a hot-shot tank gunner who has developed a risky but effective technique of firing through his own shield. In between training montages, Joe has some sentimental scenes with his kids.
Act 3: Finally, it's time for the climactic battle. Joe is assigned to drive a tank with the hot-shot gunner manning the turret. They manage to take out most of the invaders, but there's a mothership that's just too fast for the hot-shot to hit. Tragedy strikes when the tank is hit by the space invaders' lasers, killing the hot-shot. After shedding a single tear, Joe takes over his friend's turret and destroys the mothership by shooting at where it's going to be rather than where it is. Then he hugs his kids. The end.
Warner Bros., I am available!