Even those who have never read Campbells work will have probably been inadvertently influenced by the work of someone who has. For example James Cameron, writer and director of such blockbuster films as Terminator, Titanic, and Avatar.Lucas' influence on Cameron, and many other story tellers (regardless of the medium used) is far reaching, just as Campbell's work is in either a first or second hand form. As a result, there are many existing studies discussing the use of Campbell's Monomyth in contemporary books and films, such as Harry Potter, The Matrix, and other works completed long after the publication of The Hero with a Thousand Faces (Hereafter referred to as THWTF).
Tolkien's, The Lord of the Rings (Hereafter referred to as LOTR) has had just as much of an impact on story, though on a considerably wider scale. The popularity of the LOTR series vastly expanded the demand for fantasy fiction, a genre that flowered throughout the 1960s, and still thrives today. Dungeons & Dragons, which popularised role-playing games in the 1970's, features many of the races found in LOTR, such as elves, dwarves, orcs, and dragons. As a result of LOTR's influence on D&D, many video games that have been inspired by D&D contain traces of LOTR, with titles such World of Warcraft, Fable being very LOTR-esque, and of course, video games set in Middle-earth itself.
Though both authors and their work have been inarguably influential, it is important to note that neither man was influenced by the other. Tolkien completed the LOTR in 1949, as a sequel to his earlier success, the Hobbit. In the same year, Campbell released his seminal work, THWTF. Chronologically improbable, and separated by the Atlantic at a time where transcontinental communication was in its infancy, it is logical to conclude that neither author was influenced by the other in their works, and that the 1949 completion of both pieces is purely coincidental.