Save, perhaps, for his early years, Bradbury never considered himself a science fiction writer, but rather a fantasist. He used sf tropes, but was always quite willing to admit that his interest was not in the science, but the metaphoric and poetic resonances and how these could relate to the human condition.
Yet I would hesitate a very long time before agreeing that Ray falls into the category mentioned above... for much of his career, he was one of the premier writers in the sff field for both fans and critics; he also sold very well indeed to the general public. Perhaps this is in part because he emerged from the pulp field, where the strict boundaries between "science fiction" and "fantasy" were frequently ignored (Kuttner and Moore, Heinlein, etc.; even Asimov would ignore that boundary whenever it suited the tale they wished to tell)... and Bradbury never gave much of a hoot for that distinction anyway. He was also highly influenced by some of the great writers in history, American and otherwise, as can be seen by the anthologies he edited, Timeless Stories for Today and Tomorrow and The Circus of Dr. Lao and Other Improbable Stories. Ray belonged to that group of writers such as Rod Serling, Charles Beaumont, and Richard Matheson; writers taken to the collective bosom of sff fandom, but who themselves cheerfully struck out in whatever direction their muse directed... and who, as a result, were never hamstrung by any of the conventions of the field, however much they used them when appropriate.
The main problem with his work, I think, was a certain almost determined naïveté at times, and a tendency to mix the poetic with occasional passages of almost pedestrian writing... and a certain elegiac tone which can be a bit much for some.
For all that, he was, as Ellison said, a "magic man" whose like we shall almost certainly never see again, and the world is a poorer place now for his no longer being a part of it....