As a Sherlock Holmes reader, I have wondered from time to time just why the character of the Napoleon of Crime, Professor Moriarty, has become so prominent in so many Sherlock Holmes adaptations. Look at some of the most recent Holmes films and TV shows: Sherlock Holmes: A Game of Shadows included Moriarty, both Sherlock and Elementary have featured interesting twists on Moriarty (Andrew Scott's younger, crazy version and Natalie Dormer's female version), and even the recent animated film Sherlock Gnomes included an odd pie mascot version of Moriarty.
And yet, looking at the Holmes canon, it is surprising to see how seldom Moriarty is mentioned. Obviously, he features prominently in "The Final Problem." But the few other stories that mention him limit themselves to exactly that: just a mention. So the status of the Moriarty character, like that of Irene Adler, is quite disproportionate to his actual status in the canon.
I'm a stay-at-home dad, and Director of Music Ministries at a United Methodist Church in Mt. Juliet, TN, and a longtime fan of Mr. Sherlock Holmes.