Well I disagree Gondor can be really compared to Numenor.
Gondor were fighting a superior enemy (that could overpower them by numbers) and they fought to maintain their realm and ensure their safety mostly.
The Numenoreans on the other hand fought adversaries that stood absolutely no chance against them, and their only purpose was to conquer and to enslave these populations.
Though now that you mention it, I do see a resemblance between Gondor and the Roman Empire.
By conquering the area south of the Sea of Rhun and south towards Umbar, Gondor created a protection area around the core of their realm, also creating a "Pax Gondoriana".
In my opinion the same happens in the beginning of the Fourth Age.
The Reunited Kingdom (with Rohan's help) ensures for the safety of pretty much all the inhabitants of north-western Middle-earth. Even the Hobbits, the Druedain, the Dwarves of the Lonely Mountain and the Men of Esgaroth are under their protection.
It is stated that Aragorn and Eomer fought together in areas far to the east, probably in order to re-create this protectory area.
PS: I like the thread.
