It's the human race versus the Predator race versus the Alien race in Alien Vs. Predator Species Deathmatch.
One-on-one against the stealthy Predator or the relentless Alien, the Colonial Marine is only so much meat. Teamed up in an elite, highly-trained special squad of accomplished killers, the Colonial Marines are a lot more meat. It's good to see Rebellion is still giving the Aliens and Predators the bulk discount.