Teresa, good points on Isildur... especially the weregild.
Regarding Isildur... before the destruction of Numenor, Isildur's family was estranged from the rest of Numenorean society, especially the royal family. The king, Ar-Pharazon, had become the mightiest monarch the world had ever seen. He even took Sauron prisoner, but within ten years, Sauron had wormed his way into Ar-Pharazon's trust and become both Prime Minister and High Priest of the Royal Cult. Numenoreans were obsessed with immortality and Sauron played on the king's fear of death. With Ar-Pharazon cutting all ties to the past (reverence of the Angels, friendship with the Elves, and a benevolent attitude towards the Men left in Middle-earth) and Sauron declaring the unholiness of the sacred tree of Numenor, Isildur snuck into the palace one night and stole the last fruit from the three thousand year old tree. He fought valiantly and escaped to bring the fruit to his grandfather. When Numenor was destroyed a few years later, everyone praised Isildur for his forethought. The White Tree of Gondor was the product of that fruit.
And cutting the Ring from Sauron's hand, in and of itself, is the single mightiest act of any Man in Middle-earth.
Concerning Men... Tolkien's humans come in basically three branches, those who are allied with Elves (or those descended from those who helped the Elves), those who are not, and the Pukel-men or Woses. The humans who allied with the Elves of the First Age are all western European in appearance. Tolkien was writing an English mythology, so his good humans are all light skinned. They have black, brown and yellow hair. They are of middling to excessive height. They are rarely cowards, though they do not usually provoke fights. Elves referred to Men as Edain, the Second Born. But this term came to mean just the Men who allied with them during the First Age. Bor and his sons are the exception to the above physical descriptions.
In the Second Age, the Edain were given a continent away from Middle-earth... Numenor. Valinor (the land of the Valar, the Angels) was located far to the west of Middle-earth... Numenor was closer to Valinor than to Middle-earth. Thus the Men of Numenor began calling themselves the Men of the West, the Dunedain.
Other humans are almost always lumped together as Easterlings. They are swarthy with dark hair. They are of shorter stature than the Dunedain. There are also mentions of Southrons attacking Gondor. These Men are darker complexioned than the Dunedain, but not always. During the Second Age, the Dunedain had trading posts, ports, forts, and colonies all over Middle-earth. Elendil and his sons, Isildur and Anarion, were not the only high lords of Numenor to escape the cataclysm. The chiefest of the Numenorean holdings in Middle-earth happened to be the land just south of Gondor... Harad, especially Umbar. The most noble of the Haradrim were of Numenorean blood. I assume this was diluted through the years, but was renewed when the losers of the Gondorian Civil War fled to Umbar and took it about 1950 Third Age.
It may be of interest that the Rohirrim are believed by the Gondorians to have descended from a branch of the Edain who decided not to fight alongside the Elves in the First Age.
Aragorn appears to be the thirty-ninth direct male descendent from Isildur who himself is the heir of Valandil, the first Lord of Andunie. Andunie was the westernmost province of Numenor. Valandil married Silmarien, the eldest child of Tar-Elendil, fourth King of Numenor. Later, the succession laws were changed to allow females to inherit, but it was always in the tradition of Aragorn's family that even though they were not Kings of Numenor, they were the elder family... that he descended eldest child to eldest child to eldest child all the way back to Elros, the first King of Numenor. By the way, Elros was Elrond's twin brother.
The tradition of the Lords of Andunie, and after the royals of Arnor and Gondor, was to revere the Valar, befriend the Elves, and to assist the helpless humans. Their identity went back to the founders of the Edain... Beor, Marach, and Haleth. Their identity as scions of Elros was linked to the Elves. Since Elros' brother was still around six thousand years later, it's not too difficult to to see the value the Dunedain (Aragorn, Denethor, etc.) placed upon their lineage.
Oh, by the way, I mentioned Finrod in my last post. He was an Elven king who befriended Beren. He saved Beren from a werewolf, but was slain. His youngest sibling is Galadriel.
The stories of the great heroes and ancestors of Aragorn... Beren, Earendil, Isildur... these stories are not mere myths. They are not touchstones. They are fact. Living breathing fact. Beren's best friend was Galadriel's brother. Earendil is Elrond's father. Isildur stood with Elrond against Sauron. These Elves verify Aragorn's claims.
I first read The Lord of the Rings when I was fourteen. I was quickly intrigued by Fellowship, I gorged upon Towers, and about a third of the way through Return I discovered the appendices. I quit reading the narrative and read all the appendices... notes and all. It was like giving free crack to Marion Barry. I found all the history, the dates, and the backstory for which I'd been longing. (It would be another two years before I learned of the existence of The Silmarillion.) But I was horribly disappointed when I learned that following Sauron's destruction, some jerk named Elessar became King of Gondor and married Arwen. What?!?! Did Aragorn die? Was he pushed aside for some Gondorian dandy? It was not until I found, in the narrative, that Elessar was Aragorn's regnal name.
By the way... I know I've packed my posts with lots of people and places from Tolkien's writings... but believe me when I tell you that I've tried to truly simplify my explanations. I've never even mentioned Eru, Illuvatar, Aman, Beleriand, Manwe and all his buddies, Melkor, Glaurung, the Vanyar, Finwe, Olwe, Petty Dwarves, the origins of Dwarves and Ents, Draugluin, Tar-Miriel, Amandil, the voyages of Earendil, Fingolfin, the sons of Feanor, the sons of Ulfang, Estel (the name Aragorn's mother gave him), or that fact that before a flaming eye ball... Sauron used to turn himself into a wolf, a serpent, a vampire bat, the Lord of Gifts, and maybe more.