For me it's maybe the most obvious, but "Sixteen Candles". I get the appeal of "the Breakfast Club" and its dynamic between high schools stereotypes. But "Sixteen Candles" had all of that, the family dynamic with everyone gathering for her sister's wedding, the feeling of invisibility in high school and the angst of growing up, and at the same time was a high school party comedy but told from the perspective of a young woman at a time when most movies of its type were told from the "unlucky at love, who eventually finds theirs" lovable male loser perspective.
It wasn't a "girl's movie", but a movie for everyone told from the POV of a young girl. Yes, some of the humor wouldn't hold up with today's audiences. Racism/consent/high school nudity/underage drinking (it was the '80s)/etc. Molly Ringwald was her Ringwald-iest, Farmer Ted was the most iconic version of the Hughes Anthony Michael Hall geek/nerd, and if you eliminated them both it would somehow still be a very solid and entertaining version of that type of '80s high school party comedy. To me a lot of his other stuff was great, and a few came close, but this was his masterpiece.