A good writer generally inspires acclaim and appreciation; a great writer breeds division. By that litmus, Poe is certainly one of the greatest writers who ever lived. Emerson was dismissive; Huxley was sardonic; Doyle was ebullient. Even among his most ardent fans, however, there was a note of reservation, as when James Russell Lowell called him a great literary critic, if sometimes too caustic.
There are other reasons to include Poe in the front rank of fiction writers. He basically invented the detective story, and was an early pioneer of science fiction. He was also the first well-known American writer to earn a living exclusively from writing. "The Raven" remains one of the most read and most famous of American poems. But it was his short stories that really evidenced his genius.
Poe's stories were complex without being incomprehensible, dark yet not humorless, and nearly perfectly plotted.