Ah, yes, the 'hard-boiled detective' genre - I really should take a look at some of them, as it is not a genre I am very familiar with.
For a first directorial effort, 'The Maltese Falcon' is just flawless, and simply superb. Was Humphrey Bogart the first choice to play Sam Spade? Something is giving a twinge in the back of my mind suggesting that he might not have been.
Of course, the irrepressible Orson Welles also had an outstanding (and yes, flawless, too) directorial debut with the superlative 'Citizen Kane'. I remember the first time I saw it - I had feared that it would not live up to all I had read about it. But it did. It is a spellbindingly brilliant, complex, clever, fast, nuanced, highly intelligent movie, with fantastic cinematography, lighting, pacing, and is a stunning example of excellent ensemble acting and using the medium of film to tell a richly layered morality tale. I was awestruck, and could watch it again and again.