You have forgot one of the most important science fiction novel of our century '1984'. The novel itself started a new genre of science fiction and appears in almost every 'to-read' books.
Also, another sin was to not include Asimov. He was the grandmaster of science fiction and yet no attention has been paid to him.Foundation series should be on anyone's list of read if he wants to read science fiction. To be SF fan and not to read Asimov is like to be in engineering and not knowing number systems....