Obviously there are going to be differences between a literary source and the game mechanics, but of all the 1e classes Paladin is far and away the one that best represents Aragorn.
There is a good reason for this. Aragorn and the 'Paladin' have the same literary inspirations. Aragorn's 'hands of the King are the hands of healing' and a Paladin's 'lay on hands ability' have identical mythic and literary sources. Aragorn is an idealized chivilric King.
Is he a holy warrior receiving mystical abilities for faith or service in a a deity?
Yes, and in the exact same sense that the literary inspirations of the Paladin were. As the legitimate King, Aragorn is Iluvatar's appointed representative on the earth and appointed leader among mortal men. His ability to heal and command mystic forces is proof of his legitmacy not merely by blood, but by divine ordination. In Middle Earth this differs from the source material only in as much as Iluvatar is an unrevealed God, but Aragorn bears symbolicly the light which illuminates the path back to the creator through those that have born witness to Iluvatar directly or indirectly. In fact, if we read the background material in the Simirillion, we realize that Aragorn is not only the rightful heir to the throne of vanished Numernor and the subsequent Numernorean kingdoms in Middle Earth, but he is the lone rightful High Priest to Iluvatar because only the High King performed direct worship of and petition to Iluvatar. He is the High Priest and High King over the Children of Iluvatar, and through is elven linage the means by which knowledge of Iluvatar - through the Valar, thence to the high elves who had seen the light of Valinor, and thence to the decesdents of the ancient elf friends among the tribes of men - is to be brought to the rest of humanity.
Does he detect evil like a Paladin? Does he radiate a mystical circle or protection vs. evil? Can he, mystically, turn undead? Does he,mystically, heal by lay hands without material components like the 1e Paladin (as opposed to requiring a material component (i.e., kingsfoil)?
There is no reason from the text to believe that Aragorn cannot detect evil, cannot radiate protection from evil, and cannot indeed 'turn' undead. Indeed, much of what is somewhat mysterious in the text is a lot easier to explain if we assume that Aragorn in some way possesses these mystic qualities. For example, it is very difficult to explain how Aragorn drove away the assembled Nine from Weathertop and saved Frodo, when we consider that Gandalf by his own account had a great deal of trouble doing so unless we assume that there is something about Aragorn's nature as the King which caused the Ringwraiths to (seemingly) unaccountably fear him.
Granted, as with most of the 'magic' of Middle Earth, these things aren't nearly as explicit and mechanical as they are in a game and we should not expect 100% agreement mechanically with the 1e Paladin and any fictional source, but that is no reason to suggest that if you were running middle earth in D&D that the Paladin is not Aragorn's primary or possibly even sole class.
Doesn't sound like a 1e Paladin to me.
Be as that may, Aragorn is much better approximated by the 1e Paladin than the 1e Ranger. I bring this up as a testimony to how poorly most people seem to follow the text, and to point out that those people who are snearing at Drizzt because he's not a 'real Ranger' should note that because of the poor correspondence between the D&D Ranger and any of the source material and because of the prominence of D&D in shaping what people think when they think of fantasy, the D&D Ranger has become its own inspiration and its own archetypal source. Drizzt is a 'real Ranger' and Aragorn is not. The Rangers of Middle Earth are exactly what Tolkien said they were - the last remenent of the Nobility in Middle Earth. Not all those that wander are lost.
