Exclusively Extreme Competence
Where levels of skill are involved in works of fiction, it is often true that only two areas on the continuum are explored: the best of the best, and the worst of the worst. The main character will never be a "pretty decent" soldier, adventurer, marksman or what have you. He'll either be the greatest there is,
besting others in his chosen field who have been at it a lot longer than he has,
or a total incompetent, absolutely ill-matched for the position.
This extends out in circles, eventually encompassing the entire fictional world: the villain is on the protagonist's level in some facet to provide an interesting foil; the company or unit the protagonist works for is the best detective agency or elite military team of all time, since the best tend to gravitate toward the top. Likewise, in humorous situations that involve an incompetent protagonist, he's always among the worst workers at the most awful company ever.
This happens for a couple of reasons. First of all, because it tends to make a good story.
The audience wants to hear thrilling tales about bands of heroes wearing medals for bravery, not average cops filling out paperwork; even (perhaps especially) cops who know how unrealistic the former is. Second of all, audiences tend to love a winner, even while paradoxically rooting for the underdog - having everyone in the setting be exceptional fulfills both desires. Thirdly, perhaps most relevant to comedic fiction, characters who do
have mild traits of any kind tend to have them exaggerated for comedic effect
sooner or later, eventually becoming parodies of their original selves. This is inevitable as a series goes on longer.