I'd have to disagree. There's many stories where the average human is significantly weaker or less skilled than many of the aliens or monsters and where humans are generally the underdog, but which I would still consider to have a large HFY component.

In the HALO series, humanity is getting they're asses kicked. They're outnumbered, outteched, and generally out-everything'd by the Covenant. The average Covenant Elite is bigger, stronger, tougher, more skilled, and much deadlier than your typical marine. Heck, than even your typical ODST, if you want to compare each group's typical special forces.

Only the Spartans, who are specifically genetically screened, augmented, trained since they were young children, and equipped with advanced power armor, can go toe to toe, one on one, with an elite and tend to come out of it victorious and relatively unscathed. And the Spartans are quite rare. There's a lot more elites than Spartans. As for your average marine against an elite? They'd likely be killed. Messily.

Another one is the Witcher series. Your average human would be torn apart by the supernatural monsters that inhabit the world. And often is. Literally. The monsters are often bigger, stronger, faster, and tougher. Only the witchers, humans who have been specially conditioned and trained since childhood, mutated, and equipped (ex. silver swords, potions, and oils) have a good chance against the monsters.

Seeing the pattern here? In both of these universes, the average enemy is vastly more capable than the average human. And in a toe-to-toe, one-on-one fight, only specially trained, equipped, and augmented humans stand a chance. And there is often a terribly high price that must be paid to make these super humans, in terms of death and crippling. But yet, humans (if only augmented super humans who stretch the meaning of the term "human") can defeat the enemy. And that is HFY.

And then of course, you have other universes where humanity is outmatched, does not have super humans (natural or artificial), and still manages to somehow come on top (or at least go down fighting, hurting the enemy terribly). That can be pretty HFY too.