What makes a movie a "need to see"?
Well I'll put Birth of a Nation. The very first (or one of the first) feature length film. Directed by D.W Griffith in 1915, it revolutionized the way movies were made. It pioneered editing, story lines, music, costumes and especially cinematography. It's a 3 hour silent film that's as racist as anything that's ever been made, but if you want to understand how films came to be what they are today, then you need to see this film.
You know what, intercourse that. That movie is boring as hell. It's a super important film and incredibly well done, but it puts you to sleep. I still suggest you see it sometime in your life, especially if you're curious about film history or want to see some of the most blatant racism ever, but if you don't see it your not missing out.
I want to put The Godfather because if there is one movie everyone should be required to see it's that one. It's got great performances, a great story and is basically perfect. There isn't a single flaw in the movie. And atop of all that, EVERYONE loves it. It's not my favourite movie, but it's the most necessary movie.