The Predator
There was nothing "Predator" about it. You could take the entire script, the entire plot, and just switch the Predator with any sci-fi generic monster, and almost nothing would needed to be changed. No one would have noticed.
Now, how can you tell a good Predator movie? When you do the same and it completely stands out.
For example: In the original Predator, for many, what made us fall in love with it was the final fight scene. It's iconic in many ways, but without a word the way the Predator reveals himself to Dutch and takes off his armor to fight evenly matched told us so much about the core of the Predator. It wasn't a mindless monster. There is intelligence, there is a boundary not even the Predator would cross, and recognizes this human as something worthy - equal, even. This was also captured at the end of Predator 2, the fight scene in the ship and the nobility the Predators displayed towards Harrigan. They outnumbered him, but displayed greater respect for their traditions than in the mere bloodlust of the kill.
You replace any of those scenes with a generic sci-fi monster, even with the same behaviors, it wouldn't fit. Those are Predator actions, their essence, their core. Irreplaceable. We'd point and say it acts like a Predator, because we know what a Predator is and its behaviors.
The Predator? Had none of that. It was basic, superficial, and - above all- heartless. The monster LOOKED like a Predator, but it wasn't one.
