While I agree...the Alliance War doesn't particularly depict everything being as bad as the Interrgerum was made out to be, Soul Burst aside. Strikes me that as long as you aren't particularly close to the hardest struck regions (Cyrodiil), quality of life in different regions seems about what you'd expect into the late Third and Fourth Era.
Given that the ESO devs basically just said "elves", Mer in general is my guess.
I would guess that this is a safeish assumption. This isn't as applicable to between Bosmer or Dunmer (Though it could be depending on lineage), but more when comparing the Altmer to everyone else. Their stringent breeding and Altmeri culture in general is supposedly conductive to greater life expediencies then anyone else, so I would guess that the Altmer would boost longer life spans then the others because of it, if we take magical extensions out of the equation.
Culture and environment would be substantial IMO. Anyone born in a position of power would easily have much better access to medical/magical care that could keep them going on, even if they don't magically enhance their lifespans otherwise. Its the difference between an Ashlander and Barenziah, for example. As for inherited...the Altmer certainly believe in this, though how much its actually true is unknown. Are Aldmer of mixed parentage looking at a decreased lifespan? Maybe, once diluted enough. This is one of those things we just don't have good information on.
Orcs are weird, though I wouldn't put it passed anything metaphysical going on with them. As an alternative...well, just look what happened with the Falmer. Hard to imagine those poor things kicking along for even a good century.
A natural, 1,000 years is pushing it IMO. I can see Altmeri nobility and royalty, who are probably even more crazy about the racial purity thing then others, pulling it off, but the rest I would say is very, very rare.