I think the first one is quite scary, if you watch the whole movie there is a constant feel of danger and the ending at night is quite suspenseful.
Generelly Predator has more of a "cool" feeling to it, but in the first one, the creature actually feels quite scary because you don't get that much Information about it and the way it kills the guys one by one is pretty horrific with the way it moves through the jungle.
The Predator is also pretty smart, not like most movie Monsters which come right at you, the Scene for example when Dutch is luring on that tree with the fire and the Predator comes right behind him because he had the same idea, you just go like "Oh Shit".
Even the scene where he is sitting on that tree looking at the skulls of the dead men, with the Music and all, i think that is a pretty grizzly Scene, i remeber watching it in 3D with my girlfriend when the blu-ray came out and she had goosebumps when that scene came on.
I think most People just forgot how scary the Predator was at the start of the Franchise because they are just so used to it now, just like with Alien, i was afraid of it as a kid, now i'm snoring through the movie.
So, i don't really think Predator has the potential to scare the living daylight out of you, it's just not designed to be that Monster, but it certainly has the potantial to be really creepy, if you retain that feeling of the original.