Stanley Kubrick was the first director who's movies required I learn more to enjoy. After learning to understand Kubrick's movies, I enjoy all movies that much more.
I had to study Eisenstein to understand color usage. I was then able to recognize the use of color in Eyes Wide Shut. When the characters were in front of some colors, they are telling the truth. In front of others, they are lying. The use of green to signify one thing, and yellow to signify another.
I studied Bertolt Brecht to understand Verfremdungseffekt. This helped me understand the Star Child in 2001 and the bare assed bear in The SHiNiNg. I realized those scenes and images were intended to make the viewer question the directors use of the scenes, and that those were keys to understanding the movies other symbols.
I studied Kubrick the photographer to understand Kubrick the filmmaker. His photo of the news stand worker next to the F.D.R. DEAD paper told me that Kubrick used many elements in his shots to tell a story. He used everything in frame, not just the main subject to relay information.
After these lessons, along with many others, I have a better appreciation for nearly every movie I see. I see now the whole frame and what is there. I see not only where the characters are positioned, but what is around them. I see what is in the distance, what is nearby, and what the character might "really" be looking at.
After all these lessons, Kubrick has taught me how to really watch movies.