On dealing with Protagonist Syndrome

Simply put, it's trying to find the answer to the question of "Why is she the main character and not someone else?" (in my case, it's a she) Often, I've found that with a large cast, many side characters are smarter than the protagonist, more accomplished, or even simply have a more interesting skill or personality quirk, to the point that the protagonist seems bland by comparison. So how do you make your main characters stand out as special?

In my case, I've thought about her being more ambitious, more willing to take initiative in trying out big projects and crazy ideas. I wonder if that is enough.