Definites:
The Dark Knight (entertaining with very clever commentary on politics and the balance of life. Ledger with an all-time-great performance.)
Blade Runner: 2049 (beautiful and deep movie. Every note and stunning image makes you feel something; nothing is wasted.)
Avatar (groundbreaking filmography, everyone and their mother watched it)
The Big Short (should be required watch for every high school student)
Maybes
Get Out (piercing social commentary, incredibly well done in every area)
IT (I never saw it, but I heard rave reviews from everyone who watched it)
Black Panther (not my favorite superhero movie but incredible cultural significance)
Guardians of the Galaxy (IMO the best Marvel movie and the first movie of its kind)
The Social Network (never seen it in full but has the best trailer I've ever seen. I feel like it will define our generation)
EDIT: Social Network trailer
https://youtu.be/lB95KLmpLR4