There are only two reasons to watch The Thin Man: William Powell and Myrna Loy. As Nick and Nora Charles, these two actors have undeniable chemistry; so much so that they went on to appear in five sequels. (Powell and Loy would make a total of fourteen films together.)
The film itself is a relatively standard detective story. In fact, when Nick and Nora aren't on the screen — there are two long stretches in particular in which neither appear — it's downright dreary. Despite being based on a Dashiell Hammett novel, the plot is useful only in getting Powell and Loy together on the screen.
It's curious: Nick and Nora are a married couple who, despite their continual teasing (or because of it), are obviously very much in love. It's a relationship based on both respect and playful affection. It's a winning dynamic that forms the centre of the movie. And yet for some reason, Hollywood has rarely tried to repeat this formula...not with married couples anyway. The lack of strong female roles in the last few decades may be the reason Hollywood hasn't cannibalized this idea the way it has so many others. After all, there certainly hasn't been a paucity of buddy pictures between men...
The only thing that no longer works about Powell's portrayal of Nick is his constant drinking. It may have seemed like a cute, fun-loving personality quirk at the time the movie was made, but with changing perceptions and attitudes, it's difficult to watch without thinking, "Poor guy. I wonder what inner demons he's grappling with."