3. The Great Mouse Detective
It goes without saying that this is one of the best Sherlock Holmes movies, without going so far as to say this is even a legitimate Sherlock Holmes movie. After all, the protagonist is named Basil (named, of course after the actor most famously associated with the character) and happens to live, as a mouse, in the home of the great detective. He's equally as brilliant, and with his partner, Dawson, he sets out to find the kidnapped parent of his newest client. It's an inventive, twisty, fun, animated tale that sports a too-excellent-to-be-forgotten villain in Professor Ratigan (the movie's Moriarty, voiced by none other than Vincent Price) and features an exciting climatic duel between the two on Big Ben's tower, mirroring that of the great Conan Doyle short story
The Final Problem. It's the best introduction to Sherlock Holmes that you could give to a child, and one that will certainly interest them in not only some spectacular novels and short stories, but one of cinema's longest withstanding characters.