I have always stood by Turalyon as the definition of paladin. Compassionate, kind, humble, fights for justice/protecting his people/innocents and not revenge, altruistic, doesn't let anger blind him and prefers peace but is still an complete badass ready to fight and kill when no other option is available. Even at the height of his anger and watching his mentor die he decided to take the orcs prisoner and have them stand trial even when few people would have blamed him if he had ordered their extermination right there. Azeroth wouldn't exist right now if Turalyon hadn't decided to spare orcish kind despite all their crimes that day and that's a fact. Without the orcs it was almost assuredly game over at Hyjal.
Tirion is a pretty close second, but he has let anger get the best of him a few times. Still, when faced with the ancient D&D situation of a paladin being forced to choose between being lawful or being good, he chose the eternally correct answer of good. That secures him the #2 spot.
Alexandros is number three and again sharing many of the same paladin qualities as the above two, but he was a fucking crappy dad in some ways and loses points for that.
Fourth is Uther. The first paladin, the most faithful and zealous and a complete monster on the battlefield .He was no doubt a huge reason for those early victories of the Second War and I wouldn't be surprised if the survivors of those early battles told horror stories to the other orcs of this massive bear of a man glowing as bright as the sun itself smashing in heads left and right. Again shares many of the compassionate, kind, fights for justice qualities of the others but he was quite lacking in the humble department and that loses him points. Being so arrogant and self-righteous enough to believe that he had the authority to strip another person of their ability to use the Light is a further loss of points, and that is the primary reason I placed him below the others.
They are all still really pretty damn great though speaking as a massive fan of paladins in general since WC2 and D&D before that. Of course I'm not forgetting about Maraad, I love him too and wish he hadn't died solely so Yrel could take the spotlight(I don't really care for her because of that that reason amongst others, but she's still a fine character as a paladin) but I'm just talking about humans with this.
Arthas shouldn't really be on any best paladin poll. He was an above average one at best.