Dating from the days of silent films, Mr. Sherlock Holmes and Dr. John Watson have been onscreen in different forms since 1916. Over at Neatorama, you can view a video that gives brief glimpses of all the ways that the pair have been shown, from regular movies to cartoons to TV shows to re-imagined versions in other times and settings.
It's interesting, and it's also fun to try to see how many of the different versions of the character you can identify. For me, of course, one of the most obvious features of the video is the complete and utter superiority of Jeremy Brett in the role of Holmes in the Granada Television productions made between 1984 and 1994. The distinction is not at all difficult to make.
It is, in fact, elementary.