The Last Starfighter (1984)

Alex Rogan (Lance Guest) lives in a trailer park and spends his days playing the Starfighter video game. But upon meeting an alien (Robert Preston) who convinces him to use his skills in real combat, Rogan heads to space to protect the galaxy from invasion. He gets to the Starfighter base station before deciding the trailer park wasn't so bad, but returns home to find he's being stalked by an alien beast.