In defiance of popular opinion i really rate Predator 2, great film, the setting was very Robocop-esque, classic late 80's view of the future. That said the original is the best, hands down, EPIC film.
AvP films just didnt do the predators justice, because the predators are just nails, and the only other creature in the galaxy almost half as nails as a predator is a xenomorph, hence why predators make an effort to cultivate them for hunting, much better sport than just hunting humans. And all the predators in AvP were damn pussies :/