I grew up on Heinlein, Asimov, Bradbury, Clarke, Van Vogt and so on. Those were the guys I would automatically sign out from the library or buy without reading the blurbs.
Quite a few short stories from back then (some from the '40s, before my time) have also stuck with me, in a way that contemporary ones do not. Lieber's
A Pail of Air, Leinster's
First Contact, Moore/Kuttner's
Vintage Season, Bixby's
It's a Good Life, and a very dark one one whose title and author I forget at the moment, from the POV of a kid kept locked in the basement because his parents fear him for some undisclosed reason, and the first line is '"You wretch", she said.'
Those still haunt me.
Then the '60s happened and SF went to hell. Lots of LSD-inspired altered states of conciousness premises, which I viewed as fantasy tarted up to pass for SF. The science got too soft. Fortunately, Tolkien hit it big and that allowed the fantasy writers to come out of the closet and it was easier to distinguish. (Not that I didn't like Tolkien, it's in my desert island collection.)
In the '70s and '80s I bought a lot of Vonnegut, Pohl, and Niven. Went through all of the RE Howard
Conan stories, followed by all of the Burroughs'
Barsoom novels. Later on, John Brunner and Robert Forward.
'90s - Lackey's urban elves,
SERRAted Edge series. Yeah it's fantasy, but not posing as anything else.
Now I pretty much have given up on buying SF simply because it's SF, unlike in my teen/preteen years. I enjoyed William Gibson stuff, but I fear that cyberpunk themes are spoiling it again, like in the '60s. Too much like fantasy posing as SF because you cannot reasonably anticipate what any character is capable of. Magic sword, magic chip, same thing. If
The Matrix was only a book, I'd probably hate it.
Then again, I've read and re-read some of Weber's
Honor Harrington stories, simply because I like her as a character, and the technology is limited to only a few things that require willingness to suspend disbelief, and it pretty much stays the same from one story to the next. A space opera with well-defined limits to the technology. Puts me in mind of Heinlein, at times. (Waiting for the movie of
On Basilisk Station, starring Millia Jovovich as Honor. It could happen!)
Harry Turtledove is my hero now, with his alternate/fictional histories, especially the
Worldwar/Colonization series and the
Darkness series.
Somebody mentioned Librivox. Quite a few H. Beam Piper works available -
http://librivox.org/newcatalog/search.php?title=&author=H.+Beam+Piper&action=Search . I had never read any of his books, probably because I was but off by the titles and cover art, but it's okay stuff as audiobooks.
I've just started reading/recording "Planet of the Damned" by Harry Harrison for Librivox as a solo project, but it'll be a couple of months before it's complete. I must say that reading for Librivox makes me have a lot more respect for the escapepod/pseudopod readers than I might otherwise.