Jungle Hunter. He was clearly experienced based on the stories surrounding him. He stayed out of sight, waited for his targets to separate, and took them down one by one.
City Hunter may have had more toys to work with, but his style was very reckless and agressive. He was eager for spectacle.
Scar, though he managed an impressive kill of an alien, ultimately his skill seems limited.
Wolf, made some very, potentially, suicidal choices.
Feral seemed very inexperienced and, similar to City Hunter, eager for a bigger badder fight. Does not indicate high skill level.
The Bezerkers also seemed to rely more on brute force than actual skill.
Celtic showed some pretty remarkable skill given how off guard he was caught. It certainly wasn't his skill that failed him. He was observant, generally reacted fast, and deployed his limited arsenal as effectively as possible.
If I could pick an alternate Predator it would be Greyback. You can just tell by looking at the dude he's seen some stuff, has developed a high level of patience, is introspective, and probably fought many a bloody brutal fight.
