That's the aliens' problem. They're deadly in close quarters but they wilt against heavy fire power because they have zero ranged capabilty (aside from acid-spitting). If the "cleaner" pred wears acid-resistant armour, even that would be negated.
A "cleaner" pred would say "fu** hunting, this is extermination". He'd go in there with the most powerful guns, the most advanced sensors etc. and would probably have a few buddies to back him up.
He'd blast aliens with the pred equivalent of military hardware. I'm just saying that if the predators go all out, the aliens would be screwed because they simply have no tech. Tech is a huge advantage. Imagine if Celtic has a shoulder cannon when he fights Grid...
If you want a balanced fight, you'd have to keep it to a few predators hunting for sport in an evironment highly favouring the aliens. If the predators don't want to play around, they could just blow up that evironment. What I'm saying doesn't apply only to predators, Colonial Marines with some decent intel would be able to mass-slaughter aliens if the Company weren't obsessed with preserving specimens.
My point is...you fight on the aliens' terms (get into melee combat), you risk a horrible death, but advanced species have the option of not fighting on the aliens' terms.
