One of the reason why the original Predator movie was better than its sequels is the fact that Arnold was not featured in them, no one can replace the all powerful Arnold as the star of the predator. Another reason is the lack of the jungle setting in the sequels, this was a let down.
The Predator is one of the most famous movie villains: a disgusting alien whose face is incredibly ugly and therefore hard to forget. The first film in which the Predator appeared was a tightly plotted, suspenseful science fiction film, but the sequels are not nearly as good. They suffer from "sequelitis," wherein each successive sequel is a low-grade knockoff of the film that came before it.
Predator is a classic of action and horror cinema. It was made at the height of Arnold Schwarzenegger's fame and it featured excellent creature effects from the great Stan Winston. It is a badass film that plays like Rambo meets Alien. It was in desperate need of a good follow up and after several duds, Robert Rodriguez delivered a proper sequel in Predators and I hope that Shane Black, who was also in the first one, delivers another great entry.
The original Predator film was a terrific action/sci-fi movie. The later movies tried to explain too much. They are often incoherent, with little story to link it all together. The crossover with the Alien movies was ridiculous. It's time to leave this franchise behind and start looking for more innovative stories to tell.