2016 - Deadpool
Deadpool is not the typical Academy favorite. This would explain why the first movie didn't earn a single nomination. Still, that's not to say that it was left out of awards season altogether. It was nominated for Best Picture at the Golden Globes, earned Ryan Reynolds a win for Best Actor at the Academy of Science Fiction, Fantasy & Horror Films, and even won for Best Screenplay at the Empire Awards. So, there was love for Deadpool in the awards circuit - and this is precisely why it would have likely had a solid chance at earning an Oscar for Outstanding Achievement in Popular Film.
It might have faced off against movies like The Jungle Book, Rogue One: A Star Wars Story, La La Land, or Hidden Figures, but Deadpool was unique. It had the guts to hide an A-lister like Ryan Reynolds behind a mask and prosthetics, it was a major success story born out of the high hopes of passionate fans, and it turned out to be way more successful than anyone predicted. For that, it would have deserved this win; and the Academy would have likely agreed.
2017 - Logan
2017 was a tough year (for awards season, not audiences). It brought Luke Skywalker back in Star Wars: The Last Jedi, it breathed new life into Jumanji with a successful sequel, it introduced the first mainstream female superhero with Wonder Woman, and it launched the horror genre back into the Oscar stratosphere where it belongs with Get Out. That said, there was one movie that broke new mold in the Academy, earning a superhero movie its first nomination in the Best Adapted Screenplay category: Logan.
Not unlike The Dark Knight, Logan represented a major shift in the superhero genre, exploring new avenues and themes that are typically reserved for a very different category of movies. So, even though its competition would have stood a very strong chance at taking the gold, Logan was already feeling the Academy love. It only makes sense that they'd transfer the votes Logan might have gotten for Best Adapted Screenplay to this one as a kind of last-ditch courtesy.
2018 - Black Panther
Even though there is still plenty of room for other movies in 2018 to earn the Academy's first official award for Outstanding Achievement in Popular Film, Black Panther will still win. It has fellow MCU cousin Avengers: Infinity War to contend with, and Mission: Impossible - Fallout is inching to the top of the year's box office earnings, but Black Panther still has them beat. It's had too much of a cultural impact this year to be forgotten come awards season.
Black Panther broke records at the box office, it was a critical darling, and a fan favorite. More importantly, though, it represented a major shift in the racially inclusive direction that mainstream Hollywood is finally willing to go. And even though upcoming movies like Aquaman, Bumblebee, and Mary Poppins Returns may well win the hearts of many, they'll have a tough time matching the cultural weight that's associated with Black Panther. Truth be told, the introduction of this category - even though it's not the Academy's fault - isn't exactly going to start off on fair footing, which speaks volumes about Black Panther's popularity.