This is a fairly good list, although my problem with book lists this big is that there are just too many books. If I were to create a book list, I might stick to 20 being the upper limit. There are two books in SF that I openly evangelize, and will always be in my top ten SF must reads: Isaac Asimov's classic Foundation and Orson Scott Card's brilliant Ender's Game. While I can recommend Asimov's other works, I do not recommend Orson Scott Card's other books -- Ender's Game is his best, and the rest is somewhat disappointing).
I actually find myself thinking that The SF Book Club's "The Most Significant SF & Fantasy Books of the Last 50 Years (1953-2002)" is actually a much better list of SF books even though there are only half as many. I have read 17 of the 50 books on this list. There's some pop SF and Fantasy I probably wouldn't have put on this list (Terry Brooks' Sword of Shannara comes to mind).
And lastly, where is Phillip Pullman's The Golden Compass?
Hmmm, 20 on the first list, with 4 being in my possession but unread. 11/3 on the second list.
These lists point out that I'm not nearly well-read enough with Isaac Asimov, Robert Heinlein, and Philip K. Dick, among others.
Wow, some reading lists I'm finally doing well on. I got a surprising 10 on the first list and 8 on the second. And I have many of the books on both lists somewhere in my possession (or had them at some point). Hm.