Other stories ascribe some particular virtue or deficit to humanity that's often transparently influenced by the beliefs and cultural ideas of the author. Projecting American-style rugged individualism onto the entire species certainly used to be a popular one.
But really, we can pick whatever we want, because there's no way to tell. Perhaps humans are absurdly huge, and all other sentient species are about the size of a fly. Maybe we have uniquely bad eyesight, or completely lack an electromagnetic sense near-universal in other species. Perhaps we have a really weird body plan compared to everyone else.
So: Domestication of animals was a major part of human development. Dogs in particular played a very important role, being used as hunting companions, pack animals, guard animals, and more. They're so important to us that we bred them to have more human-compatible facial expressions: dogs' facial expressions are very different from wolves', and much closer to human ones, something that helps a great deal when you're trying to communicate. Likewise, dogs tend to be very attuned to their humans' mental and emotional states.
So in a sense, our civilization isn't a human one, its a human-dog one, with dogs as junior partners, and other domesticated animals like cats as more minor ones. Nor did all of this domestication necessarily go one way. If dogs form an integral part of your lifestyle, being able to interact with them well is a distinct advantage.
My idea is that co-domestication could be the norm, and humans are actually an outlier in how little of it we did. Sentient species from other planets all "grew up" in complexes of a handful to several dozen species that learned to cooperate and communicate, co-domesticating each other and fulfilling particular roles. In terms of intelligence, most species in a complex tend to have an intelligence somewhere between that of a dog and a human, with some outliers.
For the aliens, this co-domestication is the generally accepted model of how sentience and civilization arises. Humans are really confusing to the aliens because we have such an impoverished set of species around us.
When the first human spaceship finds aliens, and they come on board, we're amazed that they're four quite different creatures. We assume that this must be some kind of interstellar alliance. The aliens are quite confused why they're only being greeted by one species. When the ship's cat saunters in a little while later, they get really excited and wish to be introduced, and insist that the cat be present for all major diplomatic events...