Joan Hickson wasn't the only actor who portrayed Miss Marple however, she was the best of all. Christie herself thought of Hickson as HER Miss Marple long before the beginning of the TV series. Hickson was the ideal British old lady who grew up in the countryside during the Victorian Era. She also portrayed the spinster with perfection: although never married, Miss Marple knew a lot of things about married people.
Although books were written between 1930 and 1970, the movies always depict the events in the 1950s.
Some other Miss Marple
She was a humorous actress, and the most hilarious Miss Marple ever. Both the stories and the old lady's personality were often changed. Miss Marple was depicted as a thin person, Rutherford wasn't thin at all. Miss Marple was also a quiet person, Rutherford had an energetic personality. All in all she was not Christie's detective amateur but she was a great actress and the movies were fun.
The TV series starring McKenzie were inspired from Christie's work however the plots were entirely changed while some episodes weren't even based on books including Miss Marple (for example: "Towards Zero"). Although McKenzie's hat was the most appropriate for the depiction of the Victorian spinster, the series wasn't faithful to Christie's female crime-fighter. Most characters including Miss Marple were portrayed like lunatics, the stories were entirely changed, other characters were added - most who wouldn't have been welcomed in a 1950s society - and even some turned into alcoholics.
The newest Miss Marple is Julia McKenzie. Once again, the series includes episodes in which Marple shouldn't appear (for example "Why Don't they Ask Evans?", "The Pale Horse", etc.) The worst part of this new series lies into the fact that the producers turned the beautiful and sophisticated Julia McKenzie into a replica of Mrs Doubtfire.
Moreover, McKenzie is too young to play Miss Marple. Although Miss Marple is in her 70s, she has rheumatism, she can't move like a young woman, she's also provided a shy personality although extremely sharp and clever. The other downside of this new series is that Miss Marple acts like an actual detective.
Besides these four main Miss Marple, Angela Lansbury played the role for the movie "The Mirror Cracked from Side to Side". Ita Ever starred the old spinster in the Russian version of "A Pocket Full of Rye".
All in all if you're fan of Agatha Christie or fell for British cinema and theater, if you enjoy a good mystery, then I do recommend this TV series.