Prove it Pointy Ears! I'm a Nord and will ignore the facts! Actually, I would be very interested in finding out this actual history. Can you refer to a specific place in the Wiki so I can take a look and make myself familiar? I'm thinking about playing an Altmer on my next build.
The "Elves" are not a race. It's a generic term for several offshoots of the Aldmer. The race that was in Skyrim first were the Dwemer, followed by the Falmer. The Atmoran Nords were there before any of the existing Mer races so by you're line of thought it would be consistent to propose that they have legitimate claim over Skyrim over any existing race in Tamriel including the Altmer, Bosmer and Dunmer.
In point of fact it's central to the "we were here first" argument (which isn't particularly persuasive in and of itself) because they are completely different races and cultures. The fact that they can claim common ancestry is no more a valid basis to assert that they have a more legitimate claim than the Nords to Skyrim than someone claiming that because they had the same great great grand uncle as someone else they're more entitled to the house that another person has been living in for the past 50 years because it used to belong to that someone else who had the same great great grand uncle. It's simply not a persuasive argument.
The Dunmer would take issue with that statement. The very same Dunmer who gave Tiber Septim the means to defeat the Aldmeri Dominion. The Dunmer are the only race of Mer that were able to have its members actually ascend to divinity. The Altmer have never even come close to conquering Tamriel so attributing that as the basis for the claim that they're the most powerful of the existing elven races isn't a valid basis. Unlike the Altmer, the Dunmer were never conquered by the Empire.
The Dunmer are descended from the Chimer who emigrated to Morrowind as a direct result of the open conflict between the Altmer and the Chimer when they were merely the Velothi. The fact that they chose to join the Empire and provide Tiber Septim with the means to destroy the Aldmeri Dominion of that time is indicative of more than minor differences in beliefs.
Well it's all opinion anyway really isn't it, there's various arguments all with valid points to who has a right to skyrim and other things, theres no outright right or wrong answer which is what makes TES story so good.
The Dunmer were not all but destroyed by the Saxhleel. The Saxhleel took southern portions of Morrowind. Much of that territory was originally part of Argonia before Morrowind conquered it during the Arnesian War between Morrowind and Argonia and held by Morrowind for less than half a century. The Dunmer armies eventually stopped their advance although it's not clear what the exact borders of Morrowind look like now. We do know that Argonia controls at least up to the area of what was once Vvardenfell because the Dunmer Spellsword Sul states so in The Infernal City. Control of that area is somewhat meaningless though because it's a desolate uninhabitable wasteland since the Ministry of Truth fell from the Sky and the Red Mountain erupted, both of which did far more damage than the Accession War. While we don't know the geographic size of Morrowind, we do know it has a considerable army to have stopped the Argonian advance and we know it gained territory to the north when Skyrim ceded Solthsheim to it after the Red Year, so it's a grotesque overstatement to say that Morrowind is all but destroyed.
The Aldmeri Dominion lost every single soldier in Cyrodiil as a result. Its forces were so decimated that it couldn't even reinforce its struggling army in Hammerfell and lost all the territory it had been granted under the White-Gold Concordat to the Redguard resistance
I'm not even sure what this is supposed to mean. Hammerfell is an independent nation. That doesn't make it isolated. The borders between the Empire and Hammerfell are open. We know this because the Alik'r are allowed to move freely in most of Skyrim.
The only way one could make a statement like this is if one has never played Skyrim or they avoided the cities of Windhelm, Riften and Solitude for the entire game. There's an entire area of Windhelm populated by them. They also survived the ash scarred lands of Morrowind surrounding Vvardenfell so it's pretty clear that they're as adaptable to any climate or environment as any Mer, more so because they can move freely underwater.
The Saxhleel had the only standing army that actually repelled the Daedra invasion during the Oblivion Crisis. They actually were following the Daedra through the Oblivion Gate and the Daedra sealed the gate to protect themselves against the Saxhleel. The Saxhleel have no ambitions for world conquest but equating that to not having formidable military capabilities when needed would be a serious mistake.
