Description taken from Arcade version of this game

Released by Capcom in the summer of 1994, Alien vs. Predator is loosely based on its namesake movies Alien and Predator and has gameplay reminiscent of Final Fight. The setting is San Drad, California, the largest city on the West Coast, where the Wayland Yutani Corporation is developing biological weapons. An emergency situation occurs, and in 72 hours, San Drad is overrun by Aliens. Incredibly outnumbered, two heroes, Dutch Schaefer and Linn Kurosawa, fight the Aliens in a losing battle. When all seems lost, Predators materialize and side with the heroes to join in the "hunt" and give humans one last hope for survival.

Gameplay begins with the choice of one of four characters: two Predator and two human characters, who battle through seven stages to reach their ultimate destination, the Queen Alien. Pick up scads of weapons and powerups along the way and learn the special moves for each of the four characters as you progress through the city, ridding it of its Alien presence. ~ Paul Biondich, All Game Guide