If you've ever seen the Sherlock Holmes movies you'll notice a stark contrast between Robert Downey Jr.'s portrayal and the Detective on display in the books. In the books we have Watson describing a man he admires, an account colored by Watson's astonishment at Sherlock's genius.
In some ways this offers us deeper insight into Sherlock's methods. Often Watson compares his reasoning to the superior intelligence of Holmes. This allows the reader to understand the brilliance, and points us in the right direction.
But Watson's fawning over his friend's keen intellect often distracts the reader from key facts which are included within the narrative, and sometimes the facts are omitted in the interest of keeping the readers' attention on the Detective solving the mystery.