Lotta good authors mentioned on this thread are in my collection- Tolkein, Moorcock, Lieber, Howard, Lewis, LeGuin, Donaldson, Vance- as are many more.
But personally, I got my intro to fantasy in the same place as many of the authors themselves: the various mythologies of the world and the epic poems and stories they produced. The Illiad, The Odyssey, The Divine Comedy, The Kalevala, The Faerie Queene, Arthurian legends (like Sir Gawain & the Green Knight), The Song of Roland, Beowulf, Grimm's & even the Bible...they were the door that opened my mind to fantasy, and IMHO, are the REAL bedrock upon which our hobby rests.
I'm not saying that the fantasy novelists haven't added to the lexicon. Moorcock gave us one of the first antiheroic protagonists (Elric), Vance gave us the basic structure of D&D magic and many items (IOUN Stones, anyone?), and of course, Tolkein's reworking of European folktales into his epic LoTR was so masterful that its has become a benchmark in fantasy liturature...but without the legends of gods and demons dating back from the dawn of the written word, the modern writers would have had to do a LOT more work.