Look, this is very obvious. Predator, the 1987 original, isn't just the best Predator movie, it's arguably the best action movie ever made. It's certainly my favorite.
It's not just that Predator is a lean, incredibly tight action movie with zero fat, it's also iconic and perfectly cast. I'd argue it also features Arnold Schwarzenegger's most effective action hero performance.
Frame for frame, I'd put Predator up against any action movie ever made. It's a beautifully shot, perfectly executed exercise in taut claustrophobia. Every beat, every plot twist is perfectly timed. Watch it right now -- this hasn't aged a day.