What the Unexpected has that no other show has is a surprise ending. Okay, I should clarify... the Whistler had surprise endings; the Diary of Fate did too. But the Unexpected was not a genre program in the traditional sense. If "surprise ending" is a genre then that's where the Unexpected fits. Sometimes it was a crime/thriller show, other times a comedy program or even a romance show. Unlike the Chase, the lack of genre is not a detriment - far from it. Since every episode has a surprise ending, the climaxes land in a way other programs couldn't achieve.
To explain what I mean, I'll look at the climax of the episode "Birthday Present." All her life, a woman has been given the second-best things in life. For once she hopes her husband might give her the very best by buying her a gold bracelet, but once again she is disappointed - the gift is silver. She decides to exchange it and pay the difference to obtain the gold bracelet, only to learn the bracelet is actually platinum - her husband gave her something even more valuable than gold. She was not given second-best.
That's not an exceptional story, but it's atypical for radio. If that plot had appeared on the Whistler then it would have been much the same - except that the wife would have tried to kill or steal to get the gold bracelet, with the platinum an ironic reveal after her arrest. But the Unexpected has the most unexpected climaxes of all - happy endings! What a concept!
The Unexpected is not a very demanding program - it's short, fast-paced (certainly much better paced than the Strange Dr. Weird) and has an agreeable surprise at the end. It's unpretentious (unlike the very pretentious Diary of Fate). I like it - check it out if you like the Whistler.