Look at the Rank 5 list. Most of them were never on a fan poll. These are great books, they are becoming forgotten, except for those men and women who have the experience and knowledge to value them and write their histories. There are many ways to define the word classic. There are many kinds of memory.
Publishers can keep popular books in our memories by keeping books in print.
Critics and essayists can keep books in our memory by remembering and writing about them. Fans keep books in our memories by voting on fan polls and keeping books remembered by word of mouth.