Oi! Expert opinion here (ish), since I read the Complete Sherlock Holmes (Volumes one... and two! [of two]) at some point in junior high. It is not a ACD plot, in any way, shape, or form. Also, the series "first appeared in publication in 1888."
K so for the film: if you like witty banter and such, it abounds in profusion. And if you're into Da Vinci Code-esque secret societies trying to take over the world, well, there's that too. The plot is basic stuff: the bad guy gets away, they track him down, find some clues, banter wittily, stop the plot in the nick of time. It's basically Shanghai Knights for a slightly older audience. If you're going to make a Holmes movie, I think you really need to stick to a more 'personal' who-dunnit-y type mystery, like Arthur Cabon Doyle's favorite (according to Wikipedia) The Adventure of the Speckled Band
or even one of the novels (Hound of Baskervilles, etc.) The big international James Bond-y stuff really doesn't fly, in my opinion, not even in the serials. It's really always been a collection of mysteries; Wikipedia explains Moriarty
Doyle's original motive in creating Moriarty was evidently his intention to kill Holmes off. "The Final Problem" was intended to be exactly what its title says; Doyle sought to sweeten the pill by letting Holmes go in a blaze of glory, having rid the world of a criminal so powerful and dangerous any further task would be trivial in comparison (as Holmes says in the story itself). Moriarty only appeared in one book because, quite simply, having him constantly escape would discredit Holmes, and would be less satisfying. The Valley of Fear changes this.
Eventually, public pressure forced Doyle to bring Holmes back.
The later books mention the character a bit more, but you can't make years of barely interconnected mysteries into one film, unless the real intent here is to create a Steampunk James Bond franchise.