Predator 1 all the way. You could go on forever as to why, but the build up and delivery in that film was simply fantastic. Quick introduction and then we're moving with a great cast into a perfect location for this story. No extra baggage, no filler.
Like Alien 79, a group of folks out doing their job. Set upon by a monster that blends into the environment. And one by one, they get taken. No backup, no vehicles, no extra weapons and ammo in the trunk, no lab, no Gary Busey to explain exactly what they're dealing with.
Just the hunter, and its prey. Nothing more. It's still the only predator movie I can watch where I don't just see a yautja. It still feels like a vicious and ominous creature, more akin to the xenomorph. More scary, if you will.