Alien. Alien is so many things. It is a fantastic sci-fi movie, monster movie, horror movie. Alien, and the sequel, Aliens, are two of my favourite movies of all time.
I'm a sucker for post-apo movie. And above Mad Max Furry road (really good) , or the older Mad Max (the second mostly), and the recent Snowpiercer... I still find Waterworld endearing. F.Herbert influence on the worl building, and some nice visual sell it for me
casablanca is the best movie, pound for pound, in film history, and it represents the pinnacle of a not-really-genre i love: europeans abroad. war, colonial history, fallen glory (a la brideshead revisited), all sorts of themes a director can pull in.
Psychological. The Great Gatsby (2013) Fits what I like about movies- surprising me with something fun when I am expecting something serious. Also, I am a sucker for soundtracks. I'm torn between Predestination and Ex Machina for Science Fiction.