Somebody is always putting out lists--The Classics of Science Fiction V5 is available. They're ranked by "citations" here. As usual, their ranking bears no relationship to how I judge the books, and there's a cutoff--I stopped having so much time to read, and I didn't spend as much time browsing the SciFi shelves of the bookstore. I never heard of a lot of their titles before.
Of their 108, I read 36 that I don't care to read again. The Left Hand of Darkness was well-thought-out and well-written and it will never again bubble up to the top of my reading list. Frankenstein was fun, but once was enough. On the other hand, Childhood's End struck a kind of mythic chord--I'll never read it again (I've had kids since then, and grown somewhat myself, and I no longer like it) but I read it more than once when I was younger. 22 of them (e.g. Canticle for Leibowitz) are on that "I read it several times" list. 6 are in the never-read-and-never-will, 25 are maybe-if-it-was-handy, and the other 19 I don't know enough about--most of them are recently published, of course.
So, about 2/3 once to 1/3 many.
"Have I wanted to re-read it?" is a slippery measure for how good I think a book is. I see different things in Canticle each time I read it, but I've re-read others simply because I was in the mood for the experience I knew the book was competent to provide. (I'm thinking of H Rider Haggard here, but there are plenty of other moods.)
Now and then I have admonished some of our kids to "Read something different!" But I get it.