Oh, I should say more? Why do people here on the most part believe that individual people are able to decide whether things are good, as opposed to commitees or whatever, but not if that matter is literature? Sure, 95% of everything is crap, and people are stupid... but just because something is popular doesn't mean it isn't good. SF is the one genre that asks you, above all else, to question your believes, to ask "what if", "why not", and "who says". Sure, we have bad writers like Robert Jordan, formulaic plots like the Sword of Shannara series or anything by Mercedes Lackey. But at the same time, there are things you won't find anywhere else.
The books you listed as the "people's choices" for best of the century - I agree with most of them. (Heinlein is my favorite author but he did go nuts somewhere around Stranger in a ....).
Escapism? Brother, sometimes SF is the only thing that comes close to speaking to me. You mentioned Ender's Game - when I read that, I was 14, lonely, talented, and a little too egotistical. The characters in that story spoke to me. No, I saw myself in them. I have never been a soldier in Hawaii. I have been a child who felt adults were looking down on her. Would PJs novel have done more for me?
It ain't my novel and, yes, it would have done more for you. Read it and find out for yourself.
Again, I'll repeat. No novelist was/is more egotistical than Norman Mailer yet he even proclaimed From Here To Eternity a better novel than he could have written. It just killed him inside to admit that but Jones' novel was just that good that he had to.