From various info that I've gathered, I've come up with some fairly solid information on most races and their individual lifespans.
Altmer, Dunmer, Orsimer, and Falmer:
It is well known that these Mer races are more than capable of living for over a thousand years. I've read accounts and reports of various Altmer on Summerset Isles who are, quite literally, over 4,000 years old. Despite being cursed, the Dunmer are also blessed with a very long lifespan, as are the Falmer. The Orsimer librarian at the College of Winterhold has been confirmed to be over 600 years old as well.
It is also known that Nurelion, an Altmer alchemist located at the White Phial in Windhelm, was known to have died naturally from old age, indicating that, being a Mer, he was well over 1,000 years old. Knight-Paladin Gelebor is a Falmer who has been confirmed to be over 4,000 years old, suggesting that the Falmer were one of the longer-living races of Mer. A Dunmer wizard named Divayth Fyr is also known to be over 4,000 years old, likely using magic to extend it. The Psijic Rite Master Lachesis, an Aldmer from the First Era, was known to be at least 2,900 years old prior to his disappearance. Another reason for Mer having such long lives is Phynaster, the Hero-god of Summerset Isles, taught the Altmer how to naturally extend their life by 100 years.
Redguards, Nords, Imperials, Atmorans, and Nedes:
It has been known and confirmed by multiple sources that the races of men generally do not live for more than 100 years. It is, however, possible for a human to naturally live another 5-15 years through the use of unnatural such as magic or, likewise, natural methods to improve overall health like food and exercise. However, there are also many who have even been know to die at the age of 80 or even 60, likely due to poor health or other damaging factors.
Bretons:
Breton lifespan is arguably the most confusing in Skyrim, alongside the Argonians and Khajiit. After reading various articles, and gathering clues from in-game lore, I can safely say the Breton race has a similar life expectancy to that of an ordinary Human. There are two quotes that suggest this:
"They burn bright but quickly" Indicating the Bretons have great magical power but "burn" (die) quickly, similar to humans.
"When Cassynder assumed the throne upon the death of his mother, he was already middle-aged. Half Elven, he aged like a Breton." Referencing Cassynder, fourteenth Emperor of Tamriel, who died at the age of 55. He was not a Breton, but he was half Elven. His mother was a full-blood Dunmer, yet his father was half-Imperial and half-Altmer. Cassynder was also known to have poor health, and by the time he was middle-aged, which is generally considered 40-65 for humans, he had "Aged like a Breton."
As a final note, however, I had also read once that there was a male Breton with Vampirism who was over 300 years old, although I cannot recall the exact details. This evidence also suggests that, given the Breton's Mer blood, they are capable of extending their life beyond a normal human's, though likely not to the extent of any full-blood Mer. On the contrary, however, this long lifespan could also be caused by Vampirism, though I was unable to find any solid proof that Vampirism did indeed cause extended lifespans.
Unfortunately, I was unable to find any solid evidence for the lifespan of Argonians and Khajiit. However, I was also unable to find any solid proof that a certain factor may be damaging or extending their life, so based on that fact, it's plausible that Argonians and Khajiit, as of now, have an average lifespan similar to humans, since they lack Mer blood which is well known across Tamriel for gifting the Elves with a long life.
