Heya
Well, you're asking about what the "must read" fantasy- sci/fi stuff is and for me it's -
Robert Jordan (the Wheel of Time series)
Vernor Vinge (Fire In The Deep, A Deepness In The Sky)
Margaret Weiss and Tracy Hickman (Chronicles and Legends which are the 1st 2 Krynn Trilogies)
Raymond Feist (Magican, Silverthorn and A Darkness at Sethanon - the original Riftwar Saga)
Terry Brooks (The Sword of Shanarra and The Elfstones of Shanarra)
Stephen R. Donaldson (The Gap Cycle, The Chronicles of Thomas Covenant The Unbeliever)
CJ Cherryh (The Pride of Chanur, Devil To The Belt duology, Downbelow Station)
JRR Tolkien (The Hobbit, The Lord Of The Rings)
David Brin (the Uplift Novels),
Dave Duncan (The Reluctant Swordsman),
Issac Asimov (Foundation, Fantastic Voyage),
Lois McMaster Bujold (The Vor Game, Barrayar)
Neal Stephenson (Snow Crash),
Anne McCaffrey, (Dragonflight, Dragonquest)
Tad Williams (Memory, Sorrow And Thorn),
Jennifer Roberson, (Sword Dancer books)
Larry Niven (Ringworld, The Mote In God's Eye, Dream Park, Lucifer's Hammer)
John Varley (Titan),
Dennis L. McKiernan (Silver Call Duology, Iron Tower Trilogy),
Julian May (The Many Colored Land),
Frank Herbert (Dune),
Terry Pratchett (pretty much everything)
Terry Goodkind (The Sword of Truth series, first 3 books anyway are must read)
Arthur C. Clark (Rendevous With Rama)
Frederick Pohl (Gateway)
Piers Anthony (Split Infinity, A Spell for Chameleon, On A Pale Horse)
Robin Hobb (Assassin's Apprentice Trilogy, Mad Ship Trilogy)
Orson Scott Card (Ender's Game)
Philip Jose Farmer (To Your Scattered Bodies Go)
R.A. Salvatore (Homeland)
George R.R. Martin you already know,
David Eddings (the 5 books of the Belgariad, nevermind the 25 later books which are good reads but not great reads),
Also, I wouldn't hesitate to check out Tarzan by Edgar Rice Burroughs. Many of these popular movie things came from excellent books and it is fantasy.
Kinda like The Three Musketeers and Scaramouche - if you go by the movies, they're just adventures but if you read the books you find out 1) they're really political satire and social commentaries and very well done satire to boot. And 2) the stories are very different from the movies.
In lots of cases, just listed the 1st book in a trilogy or duology or series because if you don't like it, you won't like the others. I've read lot of other books by those authors because I loved the one I listed. In other cases, the whole series stands as one enormous story and may get continuously better as you go through it. For example Donaldson's Gap Cycle is an acquired taste in that it gets continuously better as you go on and turns brilliant in the last 2 books of the 5. In fact, Donaldson's subject matter and style are an acquired taste and not for everyone but he can paint a new world as well as anyone.