A lot of gangster films don't stand the test of time. They are slow, contain action scenes not really believable, and dialog that sounds like grandmother wrote it. Hey! Maybe she did. Even so-called classics like Key Largo, in which at one point I thought E.G. Robinson was going to fall on the floor and writhe in an excess of evil.
Bonnie & Clyde stands up. Tense, funny, fast-paced. It all works. Yes, I know Barrow's sister in law, played by Estelle Parsons seemed overly shrill at times and she hated the portrayal--the real one, not Estelle. I was impressed. Of course, I'm easily impressed by ,murderous action, or so I'm told.