I think everyone will always find the Stan Winston design as the best, because it's literially the father of the franchise.
If you were to incorporate the Predator 2 design with the technology now available, that would also look fantastic.
Even for the "Lost" predators too!
AVP gave us the pretty nifty armor design, inwhich I'm personally inlove with when it comes to drawing.
I really did hate the bulky appearance though, Paul W. S. Anderson obviously has a testicle for a brain.
AVPR gives you an Elite predator who relies on intelligence and agility insted of your typical brute strength.
The design is something I found to be influenced by all the previous Predators in the franchise.
Predators showed that Predators can look nice without netting, infact I think that was a bonus.
They worked with more flexibility when designing them, obviously just not to differ them from the Classic.
But to show a kind of "Bare" nature. I'm personally led to believe that these are like normal Predators but are mutated by self experiment. Otherwise a whole new species would be f**king retarded. But that's off topic.
All in all, I like them all for their uniqueness. I'd love to see Predator 2 with the current technology.