Perhaps. But coming from the generation of writers Ray comes from, the distinction between sf and fantasy is/was very much as he describes it. Asimov made the same distinction many, many times, as did others, including John Campbell, Jr. and Fritz Leiber. Time travel, though an accepted sf trope, is nonetheless, by most definitions, fantasy, not science fiction, as the likelihood of such ever being possible, given the laws of physics, is extremely unlikely to say the least. So, yes, "A Sound of Thunder" is fantasy, not sf.
That being said, Bradbury nonetheless is an enormously important writer in the development of sf, who influenced many who came after him. As far as picking my favorite Bradbury stories.... that's a tall order. How many are we allowed? (The man has a rather impressive list of books, don't forget....) But "The Fog Horn" and "The Pedestrian", as well as "Pillar of Fire" (the first story of Ray's I read) and "Chrysalis" all would fit into that count, I think...
I have to agree with Ellison's assessment: Bradbury is definitely a magic man....