People are always keen to tell you their top 5 "in no particular order" or mumble and mention about three films when you ask them straight out what their favourite film is. It's a very difficult thing to do, but I think everyone should be able to tell you what their favourite film is at any given moment. Maybe it changes from day to day or minute to minute, but you should have an answer ready when somebody jumps out of a train and throws the question at you.
I'll answer. My favourite film is 2001: A Space Odyssey.
The reasons are: it encompasses the birth of humanity (the "apes" look stupid but the moment when they discover tool use is perhaps my favourite in all cinema) and goes all the way to the next stage in intellectual and existential development. It is beautifully shot and the classical soundtrack (the inclusion of Johann Strauss' Waltz on the beautiful Blue Danube is genius). It deals with questions of greater depth than anything else I have ever seen (for example, human versus computer intellect, morality versus pragmatism, known versus unknown and about a million more). It also ends with one of the most ambigious and bewildering finales in all of cinema, which allows a subjective interpretation and endless speculation, which lends a great deal of mystery to the whole affair.
I'll end my love-in there. So who can pin their cinematic taste down to one single film in an unambiguous manner? Posts include references to more than one film will be booed and shunned!