I'm very picky as a reader, and though I've always thought of myself as a fan of "sci-fi and fantasy", I've really not read a ton of either.
When it comes to sci-fi, the books that I can name off the top of my head that I own are the Time Patrol stories by Anderson, Foundation series by Asimov, Legion Of Space books by Williamson, a couple by Hamilton, The Lensman series by Smith (natch
), the Terro-Human History stuff by Piper and a smattering of single books by a few others.
For fantasy my preference was always for the non-traditional, anti-Tolkien stuff. Moorcocks Champion Eternal books, Zelazny's Amber series, and then appreciating earlier and earlier fantasy works like Vance's Dying Earth books, the works of Clark Ashton Smith especially the works that inspired The Dying Earth, Zothique. Leibers Fafhrd and Gray Mouser stories, the works of Lord Dunsany (probably my favorite writer) and a smattering of one off's and anthologies.
For some reason winter has always put me into a fantasy mood, and I prefer fantasy books, shows, or video games during the cold months.
I think I lean more towards "fantasy" (really more New Wave or Dark Fantasy) than sci-fi. I've little interest in most modern fantasy (that includes the bulk of stuff written for the last 30 years) as most has seemed way too derivative of Tolkien, is the same tired old story, or is some jack ass trying to show that he can out world build Tolkien by giving us a level of insanely inane details about the most mundane shit.
But I really don't read all that much these days. As for recommendations, well I don't really have any for sci-fi as most of the stuff I like is old and most modern audiences may not take to it. Ditto for the fantasy that I like.
Though if I were to recommend any fantasy, I'd recommend Lord Dunsany. He was the biggest name in fantasy pre-Tolkien, is a huge influence on Neil Gaiman (Stardust is a major homage to Dunsany), was a big influence on Lovecraft as well.
The guy's writing was magical in itself and many have tried to copy it's style, usually failing. Simple, elegant, whimsical and always beautiful.
“And little he knew of the things that ink may do, how it can mark a dead man's thought for the wonder of later years, and tell of happening that are gone clean away, and be a voice for us out of the dark of time, and save many a fragile thing from the pounding of heavy ages; or carry to us, over the rolling centuries, even a song from lips long dead on forgotten hills."
“If one who looked from a tower for a new star, watching for years the same part of the sky, suddenly saw it (quite by chance while thinking of other things), and knew it for the star for which he had hoped, how many millions of men would never care?”
“Once I found out the secret of the universe. I have forgotten what it was, but I know that the Creator does not take Creation seriously, for I remember that He sat in Space with all His work in front of Him and laughed.”
“There is indeed a great deal of futility amongst the human race which we do not commonly see, for it all forms part of our illusion; but let a man be much annoyed by something that others do, so that he is separated from them and has to leave them, and looks back at what they are doing, and he'll see at once all manner of whimsical absurdities that he had not noticed before; and Ramon Alonzo in the shade of his oak, waiting for the noon to go by, grew very contemptuous of the attitude that the world took up towards shadows.”
My favorite quote of his
“All we who write put me in mind of sailors hastily making rafts upon doomed ships. When we break up under the heavy years and go down into eternity with all that is ours our thoughts like small lost rafts float on awhile upon Oblivion's sea. They will not carry much over those tides, our names and a phrase or two and little else.”