Aragorn was not strong enough to wear to One ring and he knew it. That's why he was the first one to support Frodo in his quest.
When Boromir fell, Aragorn refused again to take the ring. I believe Sam could wear the ring, too. Both Frodo and Sam had the innoncence to protect them long enough and destroy the ring.
I'd like to discuss Aragorn's strength. If you don't want to read this entire post, then let me just say that Clansman has summed up my thoughts in his last post.
I firmly believe that Aragorn was strong enough to wear the One Ring. This is why Sauron was so frightened of him. In the short term, Aragorn's righteous zeal would've swayed even more descendents of the Edain to his banner. In the short term, Aragorn's grip on reality would be sufficient for him to use the Ring to empower his Numenorean gifts to attack the Barad-dur itself. With the Ring, Aragorn may have been able to reduce the foundations of Barad-dur to rubble.
The issue is not whether Aragorn had the strength of mind and body to use the One Ring, he did. This is proven by Sauron's hasty assault after Aragorn revealed himself in the palantir. Aragorn resisted Sauron's gaze and then used the palantir independently of Sauron. Sauron launched his war prematurely just to deprive Aragorn the chance of mustering a host. He thought Aragorn might not yet have the Ring... the war was to also drive Aragorn back from linking up with the Hobbits if they still had the Ring.
Having the opportunity to gain the One Ring was Saruman's secret lust, Galadriel's greatest test, and Gandalf's darkest fear. Sauron rightly feared any of them wielding his greatest weapon against him.
Aragorn knew he was not strong enough to resist Sauron in the long run. He knew if he claimed the Ring that after many years It would turn him into an evil tyrant.
Aragorn was also intelligent enough to realize that might not even live that long. The Ring betrayed Isildur to his death in less than three years.
Aragorn and Faramir learned the lessons of the Eldar and the Edain well. Feanor, the sons of Feanor, Thingol, Hurin, Turin, Eol, Turgon, and Earnur all had their hopes dashed at one point or another by taking short cuts, not heeding the wisdom of the Valar, being over proud, or listening to the enemy. Denethor, Boromir and Theoden followed in their footsteps... but Boromir and Theoden threw off their despair and fought valiantly to the end.
If Aragorn had taken the One Ring, he'd have followed the villainous paths of Feanor and Turin. He did not because his idols were Beren and Earendil. Elrond and Gandalf, his tutors, taught him well. And it helped that he was loved by a woman who would never hold a thought about following any lies of Morgoth.
KESpires, the rangers of the north were all Numenoreans. They were the last remnant of the Numenorean kingdom of Arthedain, i.e. the loyal Numenoreans who resisted the Witch-king's destruction of Arnor.
The rangers of Ithilien were Gondorians. The original Gondorians were Numenoreans, but after three thousand years they'd intermarried with the men of middle-earth and had drawn in large populations of non-Numenoreans into Gondor.
In Frodo's time with the rangers of Ithilien, four of them are named... Feanor, Mablung, Damrod, and Anborn. Feanor is a son of the House of Hurin (the most ancient, noble, and powerful family of Numenoreans left in Gondor). Mablung is presumably named after the Sindarin hero of the First Age... if he is, then there's a good chance he's of Numenorean descent. My knowledge of Westernesse and Sindarin are limited but I'll attempt to speculate upon Anborn and Damrod. I believe in Sindarin 'an' means long and 'born' means tree... thus Anborn could mean long-tree and show that he is of Numenorean blood. On the other hand, I cannot read anything into Damrod, except that the sixth son of Feanor was named Amrod... that's not conclusive at all.