WorldCat Identities top 100
According to WorldCat 100 Identities, the two biggest authors in world literature, according to library books representation, are: William Shakespeare and Johann Goethe, respectively. [2]
In intellectual rankings, greatest literary author ever is an epitaph given to a person, depending on ranking methodology, some rankings of which are listed below, that classify, list, or describe someone as being the greatest author of world literature of all time.

WorldCat Identities
See main: WorldCat 100
The WorldCat 100 rankings lists the top 43 literary authors of all time, ranked by world library holdings, according to 2011 WorldCat Identities library rankings, as culled from the top 100 identities (shown adjacent) of the worlds libraries, non-literary authors removed:

US Street poll | 2012
The following are the ranked results of a 2012 informal polling of 54 average Americans, in Chicago, who were asked to provide three names of people who they considered to be the three greatest literary authors of all time (numbers in brackets being vote count): [1]

1. William Shakespeare (18)
2. Ernest Hemingway (16)
3. Mark Twain (11)
4. Scott Fitzgerald (9)
5. Charles Dickens (8)
6. Dr. Seuss (8)
7. Edgar Allen Poe (7)
8. J.K. Rollins (7)
9. Stephen King (6)
10. Jane Austin (4)
11. Walt Whitman (3)
12. William Faulkner (2)
13. John Milton (2)
14. Fyodor Dostoyevsky (2)
15. J.R.R. Tolkien (2)
16. J.D. Salinger (2)
17. Charlotte Bronte (2)
18. Ayn Rand (2)
19. Roald Dahl (2)

Other voted candidates, with one vote, in no particular order, are: Johann Goethe, Leo Tolstoy, Jean Auel, Janet Evanovich, Barbara Kingsolver, James Joyce, Nikki Giovanni, Richard Wright, Robert Frost, Francis Fitzgerald, Agatha Christie, John Keats, Margaret Mitchell, John Steinbeck, Joyce Carol Oats, Sherwood Anderson, John Dunn, John Carpenter, Louis Carol, R.L. Stein, Daniel Steel, Dante, Nicholas Sparks, Jean-Jacques Rousseau, Art Spiegelman, Karen Abbott, Homer, Thomas Hardy, Stephen Chbosky, Oscar Wilde, Louisa May Alcott, Chaucer, Silvia Platt, Tony Morrison, Kurt Vonnegut, C.S. Eliot, Julies Vern, Harper Lee, George R.R. Martin, Paulo Coelho, Moliere, Aesop, Herman Melville, Octavio-Paz, Suzann Collins, Jack London, John Grisham, Harper Lee, and Ralph Emerson.

Discussion
One salient observation noticeable, between the two rankings, world ranking and US common opinion ranking, is that although both listings have the common names of Shakespeare, Twain, and Dickens in the top, the number two ranked world author "Goethe" is strikingly missing from the US cultural mind. In fact, the only reason Goethe found his way into the US polling owes to the fact that Libb Thims, the poll data collector added in his three tentative votes of Goethe, Tolstoy, and Mitchell, into the running. Most Americans have never even heard of Goethe let alone pronounce his name correctly, for those few who do know him. American lawyer-author philosopher Daniel Spiro comments on this as follows: [3]

"Words like 'great' and 'genius' could aptly be used for but a select number of artists–for Michelangelo or say Shakespeare. In the United States, the works of these great artists have been incorporated into popular culture as the epitome of visual and linguistic beauty. By contrast, on these shores, Goethe's works remain largely unread and rarely discussed except among college students, most of whom develop a healthy dose of amnesia shortly after graduation."

One possible explanation as to why this is so could possibly have something to do with a carry-over aversion to anything German by Americans in the aftermath of WWI and WWII. The fact that American Ralph Waldo Emerson, who rose to literary fame prior to WWI, was a Goethean philosopher, would seem to corroborate this possibility. Whatever the case, it is indeed a puzzling paradox? The obliviousness of Americans to genius, literary, scientific, and philosophical, of Goethe is so pronounced that, to exemplify, it took American electrochemical engineer Libb Thims eleven years and nearly 1,000-books to find Goethe, which he did in 2006, following a decade of search and research for the person to have applied chemical thermodynamics reaction prediction methods to human chemical reactions (see: Thims history), where prior to this he had absolutely no idea who this "Goethe" person was, but has since amassed about a 30-book Goethe library collection surrounding his work, similar to Einstein who had a 52-volume collected set of Goethe's work (along with a bust of him); or possibly similar to Nietzsche who stated that the "best German book there is" was Johann Eckermann's Conversations with Goethe.

Quotes
The following are relevant and or representative quotes:

“Charles LaPorte points out that Swinburne is both continuing a tradition of Victorian bardolatry with constructed Shakespeare as the ‘greatest author ever’, while deliberately invoking the idea of ‘one book’ which civilization cannot afford to lose, only to replace its familiar referent, the Bible, with Shakespeare.”
— Travis DeCook (2011), “Apocalyptic Archives” (Ѻ)

Goethe was raised to the rank of Shakespeare.”
Henry Adams (1907), The Education of Henry Adams

References
1. Thims, Libb. (2012). “Poll [N=54]: Who Are the Three Greatest Literary Authors of All Time?”, Institute of Human Thermodynamics, Chicago.
2. WorldCat Identities – Home.
3. Spiro, Daniel. (c.2005). “Remember to Live! The Philosophy of Johann Wolfgang von Goethe”, talk delivered at the Washington, D.C., Spinoza Society, Goethe-Institute.

Further reading
● Hubbard, Will and Carnevale, Alex. (2009). “The 100 Greatest Writers of All Time”, ThisRecording.com, Aug 03.

External links
The 100 Best Books of All Time – Wikipedia.

TDics icon ns