Granted I haven't seen every bit of directing great Robert Altman's work, I would have to go ahead and say The Long Goodbye, starring Elliott Gould, has to be his best work, for a few reasons. For one thing, it really gets into his idea and/or theory of making small parody-esque references throughout the films; and this one obviously pokes minor fun with the old 50s gangster movies, as Phillip Marlowe (Elliott Gould) is meant to strike people as a 50s detective stuck in the 70s. The second reason behind all of this is that this movie seems to capture pieces of every generation; from that one, to twenty years prior. And the third reason would be, simply put, Marlowe is the ultimate badass (aside of Jason Bourne, of course).
Phillip Marlowe is a 50s character trapped in the 70s simply because of the way he goes about his business. Wears a suit everywhere he goes, seems to be very low key everywhere he goes, and carries around the persona of a 50s detective, which can be best seen in the scenes where he is looking for the husband of Eileen Wade in the hospital, where he stops at nothing to find what he needs to find, but in a very sly manner. When he sees the hippies, he acts very nonchalant, talks to them as if they are fully clothed. Very sly, cool guy; just like someone from a 50s detective thriller.
For the 50s, that's been covered in the previous paragraph. Marlowe and the way he carries himself gives you a great sense of the decade and the type of cops portrayed back then. For the 60s, you have Marlowe's neighbors, the naked hippie chicks. Very psychedelic, very attractive, and very, very high. They give you a great taste of the counterculture movement in the shorts stints they get in the movie. And lastly, the 70s. The movie takes place in this decade, there are plenty of things that show it off. The fashion (excluding Marlowe), the home setups, etc.
Phillip Marlowe being a badass should be self explanatory for anyone who has seen the movie. Enough said.
