For me at least, it doesn’t even have anything to do with Deadpool in and of itself: I liked the movie just fine, and thought it was really well done for what it was trying to be. But, ultimately, if the film gets a Best Picture nomination, I just get frustrated at the other, better films that really should have been rewarded.
The Dark Knight. Captain America: Civil War. The Avengers. Spider-Man 2. Kingsman: The Secret Service. Scott Pilgrim vs. The World. Kick-Ass.
All comic book movies, all big and all (or at least most) were very popular with the masses. And if Deadpool gets a nomination and none of these films do, history will question exactly what was present in Deadpool that made it so much better (in the Academy’s eyes, at least) then those films. And I literally couldn’t begin to tell you what that is, other than perhaps a neat marketing campaign.