I think of all the SciFi writers I've read I put him as by far the best general writer of all of them. I read F451 looking for escape and adventure and was shocked at what I got instead.
His Martian Chronicles stories explore colonialism and make Asimov's Robot novels look simple.
The Illustrated man further expand on ideas in Martian Chronicles and mix in ideas he had with Something Wicked this Way Comes which, like F451, is AMAZING! It deals with issues with happiness and aging.
Finally, his Dandelion Wine, not SciFi, is a fantastic coming of age story, not clicheed like Stand By Me.
I think in Bradbury, like the Westerns of the '50's, you have the maturing of a genre - the human complexities of them outway his peers. Frank Herbert, HG Wells, Rod Serling, Alfred Bester, Philip K Dick - of all those great writers I think only the main works of Bester and Herbert equal or surpass his. None of them are as easy to relate to.