I disagree. There are some that I remember very well after nearly 30 years, and I expect I'd still be impressed by those today. I don't read SF much these days - usually only when something my kids have checked out is lying around.
“De gustibus non disputandum.” If you liked them, and found them memorable, than they were for you. I did not.
I was much more active in SF Fandom back in the day, when the “New Wave” was still new, and still making waves. I even reveiwed books and movies for our local fanzine (the same way Harlan got his start). I recall not everybody agreed with my tastes then, either.