Hercules had a divine parent. Not sure how the other two are different from other Greeks in a way that makes them a different order of being.
Atalanta was literally the fastest runner alive, such that she had to be "tricked" (some versions, she willingly stops to get the apples because she's decided Hippomenes is actually pretty cool) in order for anyone to beat her at a race. And she was raised by bears.
Odysseus was explicitly called (in Latin)
Ulixes sapientissimus graecorum, "Odysseus, wisest of Greeks" (though a more meaning-for-meaning translation would be
craftiest of Greeks.) He alone manages to succeed on things like nighttime raids on the Trojans without complications, amongst various other things. (Technically, Odysseus' grandfather was Hermes, but he's never presented as being part-divine in the text despite this connection.)
The point was that these people were heroes in the ancient sense of that term: larger-than-life people who had the power to change the world, but who were consequently in grave danger of hubris due to thinking themselves superior to the gods. People who
could in fact be picked out from a crowd, because they could survive things nobody else could, because they were supremely skillful or knowledgeable or magically-powerful. You also have Medea, presented as the entirely-mortal daughter of Aeëtes of Colchis, who simply gets some material assistance from her actually-divine grandparent, Helios.
Even in context, despite the genuine belief that many of these people were real
and that they died mortal deaths, so they weren't even (initially) gods, they were understood to be larger-than-life. They were understood to be people you could pick out from the crowd. And after they did die their mortal deaths, they were often deified, as I noted, literally receiving
apotheosis, "being raised to godhood", from the people who venerated them. As an example, Hercules' half-nephew and lover Iolaus (yes, it's incest, this was not considered an issue at the time) was 100% human, and yet he was deified thereafter. Gay couples would make offerings at the site of his tomb in the hopes that their love would earn divine favor.
Or Psyche: 100% mortal human, but literally so beautiful that people started to worship her instead of Aphrodite, which is what gets the whole Eros and Psyche story rolling. She's so mortal,
we never even learn her parents' names, because they literally don't matter to the story. Nor do the names of her sisters matter. Her marriage to Eros is implicitly illegitimate because it's a god marrying a mortal (understood at the time to be analogous to a freedman marrying a slave, legally impermissible). Zeus fixes the problem, giving Psyche nectar and ambrosia, the drink and food of the gods, transforming her into a goddess herself--but instead of having the feathered wings that the gods were depicted with, Psyche always has butterfly wings.
Soooooo...yeah. It's pretty much what a classical "hero"
is. Someone who stands out against the background. As
@Chaosmancer said, one gives the game away by saying "assuming those Elves are of the same class, age, abilities, etc." It is having those powers that MAKES the classical hero distinct from ordinary people. Psyche's beauty isn't actually divine, she was just born with beauty so great it makes folks question whether Aphrodite is really all that worthy of worship. Iolaus was effectively 100% mortal, but he was sort of the patron hero-deity of gay men. Odysseus and Medea were effectively purely mortal people who simply were really
smart and, in her case, trained in how to use magic. (Note that it was
training, not in-the-blood power, which is why Medea isn't a goddess but Circe, her aunt, is.) By Greek standards, even rat bastards like Sisyphus were heroes, he just fell prey to hubris from thinking his intelligence meant he was above the (sacred) law.
The modern, post-Christianization meaning of "hero" is someone who is self-sacrificing or morally upstanding in some special way (usually bravery, compassion, and/or justice), one who embodies the love and virtue of Christ. That's not particularly relevant here, since the exact same person can be heroic or unheroic (or even villainous) purely based on whether they make pro-social or anti-social choices. To the ancient Greeks, it didn't matter whether a hero was good, bad, or indifferent. What mattered was that ability to reach out and
change the world, for good or for ill.
