There are other spies in movies and books, but Ian Fleming's James Bond is by far the most famous spy of all time. Children pretend to be James Bond when they are spies, and generations upon generations of people, when asked to name a spy, think first of James Bond.
It's pretty tough to argue unless you stretch the definition of a spy. I mean, Sherlock Holmes does a lot of spying work, but I'd say that's more sleuthing than spying. In the public consciousness of what a spy is, James Bond is far and away the most popular. It's also hard for a real-life spy to be more famous, because if they are, they're not a very good spy!
James Bond is the most famous spy of all time, because he is known and loved around the world. James Bond is the icon of the United Kingdom. He was even mentioned in the opening ceremonies in the 2012 Olympics. People across the pond in the United States also think that he is an icon.
When one thinks about a famous spy, the first name that comes to mind is James Bond. It is hard to even think of another two or three famous fictional spies. He is not only well known in literature but in film, through music and in many different countries around the world.