The Conjuring. It's prob the best modern horror movie.
A Nightmare on Elm Street is one of the top 5 horror movies ever.
The Fly (80's) Can't really call this underrated, but not a lot of mentions, and it's David Cronenbergs most popular, and arguably best, film.
The Haunting, if you guys actually like good older films. I like to rewatch this every now and again. That's saying something (for me). Also toss The Innocents in. Both 1960's
The Godfather franchise, if you can sit through it.
Edge of Tomorrow is great modern action/scifi.
Toy Story franchise is awesome, and great for the summer..
American Beauty is a movie I used to watch constantly, several years ago. It 's popularity seemed to garner some negative backlash, though. I still loved it. Haven't watched it in a few years. Kevin Spacey is the man.