1. Sherlock Holmes
Holmes has to be the greatest fictional Londoner because there is now a part of London that IS Sherlock Holmes. Baker St has its own Tube station (covered on the inside with depictions of the man), surrounding which are Sherlock Holmes hotels, museums, statues, and tourists making a pilgrimage to 221B. It can be argued that he was the world's first true superhero, with beyond-human perceptive powers, a sidekick, and a supervillain. His popularity is such that he's the most portrayed movie character of all time (with 70 actors playing him in 200+ films), and shows no sign of slowing down. Mr. Holmes, London salutes you.