"Predator" is my favourite movie. I also love the second film, and I thinks is a great sequel, but the jungle, Arnold and all that stuff was just amazing.
I remember when I was a little kid I was very afraid of this movie even though Schwarzenegger was my favourite actor that time. I watched in for the first time maybe 10 years ago and from that time it's, in my opinion, the best sci-fi movie ever.
Then I've watched "Predator II" and despite the fact that the movie was completely different I loved it from the first sight, but still think that the first is the best.