Not only do Steve McQueen and Faye Dunaway give superb performances, the heist is skillfully executed, the cat-and-mouse plot/storyline is clever and cinematography great. Of course, don’t forget the film’s score!
For me, the movie has several messages. First, people’s lives need purpose. Second, never mix business with pleasure. Third, the best laid plans can come to nought.
Perhaps “imprinting” has something to do with my choice. The 1968 version of this movie, which I saw in my early teens, is far better than the 1999 remake, IMHO.