I will list some of the authors I found good.
Fantasy
Have you read any of the works from Guy Gavriel Kay? He is a Canadian fantasy author best known for his trilogy "The Fionavar Tapestry" and two books which make "The Sarantine Mosaic". He is a good fantasy author which even helped with the legacy of the great J. R. R. Tolkien.
Then there is Tad Williams with his more known works - the "Memory, Sorrow and Thorn" trilogy and the four books of the "Shadowmarch" series and various other books.
Terry Pratchett is also well know and funny as hell to read with his satirical portrait of usual fantasy themes. He has so much works that listing them all would be pointless.
Chris Wooding - Although aimed at older teenagers his "Broken Sky" series show a unique mix of anime/manga and western elements in one action packed adventure. Not sure how attractive it would be to you but you never know until you start reading. As for his other works - well I am still sad that I live in such a behind-everything place that I can't read them.
J. R. R. Tolkien - Explanations not needed. The first books I read completely and on English was the very trilogy of the "Lord of the Rings".
Science Fiction
Isaac Assamov - you have to read Assamov at some point of life to call yourself a real fan of science fiction due the she importance of his books, especially the Foundation series.
Ray Bradbury - For now I read "Cat's Cradle" and "Fahrenheit 451". If I manage to get my hands on more of his novels I will probably read them.
Lois McMaster Bujold - Best known for the Vorkosigan Saga.
Arthur C. Clarke - I don't need to explain why he is here.
Robert A. Heinlein - With Assamov and Clake he made the so called "Big Three" of their times AKA the three most important SF writers of our time. I didn't have the opportunity to read a lot of his novels except for "The Moon Is a Harsh Mistress" and the fact that I watched the movie adaptation of "Starship Troopers".
Larry Niven - I heard about him but still haven't read something from him.
Gorge Orwell - If nothing else due to "Nineteen Eighty-Four".
Kim Stanley Robinson - One of the best writer in the terms of mixing soft (social) and hard (scientific) science fiction in his Mars trilogy which is also one of the most glorious and realistic displays of a possible transformation of Mars joined with a show case of possible future technology. A must read.
H.G. Wells - A honorary position for one of those which paved the way for modern SF.
Jules Verne - Probably one of the most influential writers of his period and a predecessor of modern science fiction. His adventurer novels are rich in actual scientific techniques, terms and methods as well as well-made guesses about future possible technologies.
Dmitry Glukhovsky - The guy who wrote "Metro 2033" and "Metro 2034". You mid find them familiar due to the two novels being made into games.
Other Fiction
Clive Cussler - Dirk Pitt Adventures. Why? Well let's say that when you add evil organizations, humor, action and a government organization dedicated to studying the oceans you get a good mix. Oh not to mention they actually go and rise the one and only "Titanic" from it's watery grave in one of the novels.
Haruki Murakami - He's works are in one work as weird as you would expect from a surrealism writer.
Paulo Coelho - I will admit that I read only "The Alchemist". Trough it was a interesting read.
Stieg Larsson - The author of the "Millennium trilogy" and a strong anti-fascist. " The Girl with the Dragon Tattoo" rings a bell?
Markus Frank Zusak - The author of the "Book Thief" a strong novel about a girl living in WWII Germany and risking her life to save books from Nazis.
And that is all I can think for now. Dunno if you read any of this but this is what is enough strong to make me remember it even now so they are all pretty good. Might remember something else but that is all for now.