Top 50 20th Century Fantasy novels from Locus
Obviously some recent films may have something to do with the ratings. Bold(35) if I've read them, italics(3) if I've only seen the film (or TV show).
1 Tolkien, J. R. R. : The Lord of the Rings (1955)
2 Martin, George R. R. : A Game of Thrones (1996)
3 Tolkien, J. R. R. : The Hobbit (1937)
4 Le Guin, Ursula K. : A Wizard of Earthsea (1968)
5 Zelazny, Roger : Nine Princes in Amber (1970)
6 Lewis, C. S. : The Lion, the Witch and the Wardrobe (1950)
7 Mieville, China : Perdido Street Station (2000)
8 Rowling, J. K. : Harry Potter and the Philosopher's Stone (1997)
9 Crowley, John : Little, Big (1981)
10 Adams, Richard : Watership Down (1972)
11 Goldman, William : The Princess Bride (1973)
12 Martin, George R. R. : A Storm of Swords (2000)
13 Beagle, Peter S. : The Last Unicorn (1968)
14 White, T. H. : The Once and Future King (1958)
15 Pratchett, Terry (& Gaiman, Neil) : Good Omens (1990)
16 Kay, Guy Gavriel : Tigana (1990)
17 Gaiman, Neil : Neverwhere (1996)
18 Wolfe, Gene : The Book of the New Sun (1983)
19 Vance, Jack : The Dying Earth (1950)
20 Bulgakov, Mikhail : The Master and Margarita (1967)
21 Rowling, J. K. : Harry Potter and the Goblet of Fire (2000)
22 Tolkien, J. R. R. : The Silmarillion (1977)
23 Leiber, Fritz : The Swords of Lankhmar (1968)
24 Jordan, Robert : The Eye of the World (1990)
25 Donaldson, Stephen R. : Lord Foul's Bane (1977)
26 Bradbury, Ray : Something Wicked This Way Comes (1962)
27 Peake, Mervyn : Gormenghast (1950)
28 Rowling, J. K. : Harry Potter and the Prisoner of Azkaban (1999)
29 Powers, Tim : The Anubis Gates (1983)
30 Martin, George R. R. : A Clash of Kings (1998)
31 Bradley, Marion Zimmer : The Mists of Avalon (1983)
32 Hobb, Robin : Assassin's Apprentice (1995)
33 Pratchett, Terry : The Colour of Magic (1983)
34 Holdstock, Robert : Mythago Wood (1984)
35 King, Stephen : The Stand (1978)
36* L'Engle, Madeleine : A Wrinkle in Time (1962)
36* Pratchett, Terry : Small Gods (1992)
38 Ende, Michael : The Neverending Story (1983)
39 Peake, Mervyn : Titus Groan (1946)
40 Howard, Robert E. : Conan the Barbarian (1950)
41 McCaffrey, Anne : Dragonflight (1968)
42 Orwell : George : Animal Farm (1945)
43 Feist, Raymond E. : Magician (1982)
44 Silverberg, Robert : Lord Valentine's Castle (1980)
45 Lovecraft, H. P. : At the Mountains of Madness (1936)
46 Swanwick, Michael : The Iron Dragon's Daughter (1993)
47 King, Stephen : The Shining (1977)
48 Garcia Marquez, Gabriel : One Hundred Years of Solitude (1970)
49 Saint-Exupery, Antoine de : The Little Prince (1943)
50 Hughart, Barry : Bridge of Birds (1984)
1 Tolkien, J. R. R. : The Lord of the Rings (1955)
2 Martin, George R. R. : A Game of Thrones (1996)
3 Tolkien, J. R. R. : The Hobbit (1937)
4 Le Guin, Ursula K. : A Wizard of Earthsea (1968)
5 Zelazny, Roger : Nine Princes in Amber (1970)
6 Lewis, C. S. : The Lion, the Witch and the Wardrobe (1950)
7 Mieville, China : Perdido Street Station (2000)
8 Rowling, J. K. : Harry Potter and the Philosopher's Stone (1997)
9 Crowley, John : Little, Big (1981)
10 Adams, Richard : Watership Down (1972)
11 Goldman, William : The Princess Bride (1973)
12 Martin, George R. R. : A Storm of Swords (2000)
13 Beagle, Peter S. : The Last Unicorn (1968)
14 White, T. H. : The Once and Future King (1958)
15 Pratchett, Terry (& Gaiman, Neil) : Good Omens (1990)
16 Kay, Guy Gavriel : Tigana (1990)
17 Gaiman, Neil : Neverwhere (1996)
18 Wolfe, Gene : The Book of the New Sun (1983)
19 Vance, Jack : The Dying Earth (1950)
20 Bulgakov, Mikhail : The Master and Margarita (1967)
21 Rowling, J. K. : Harry Potter and the Goblet of Fire (2000)
22 Tolkien, J. R. R. : The Silmarillion (1977)
23 Leiber, Fritz : The Swords of Lankhmar (1968)
24 Jordan, Robert : The Eye of the World (1990)
25 Donaldson, Stephen R. : Lord Foul's Bane (1977)
26 Bradbury, Ray : Something Wicked This Way Comes (1962)
27 Peake, Mervyn : Gormenghast (1950)
28 Rowling, J. K. : Harry Potter and the Prisoner of Azkaban (1999)
29 Powers, Tim : The Anubis Gates (1983)
30 Martin, George R. R. : A Clash of Kings (1998)
31 Bradley, Marion Zimmer : The Mists of Avalon (1983)
32 Hobb, Robin : Assassin's Apprentice (1995)
33 Pratchett, Terry : The Colour of Magic (1983)
34 Holdstock, Robert : Mythago Wood (1984)
35 King, Stephen : The Stand (1978)
36* L'Engle, Madeleine : A Wrinkle in Time (1962)
36* Pratchett, Terry : Small Gods (1992)
38 Ende, Michael : The Neverending Story (1983)
39 Peake, Mervyn : Titus Groan (1946)
40 Howard, Robert E. : Conan the Barbarian (1950)
41 McCaffrey, Anne : Dragonflight (1968)
42 Orwell : George : Animal Farm (1945)
43 Feist, Raymond E. : Magician (1982)
44 Silverberg, Robert : Lord Valentine's Castle (1980)
45 Lovecraft, H. P. : At the Mountains of Madness (1936)
46 Swanwick, Michael : The Iron Dragon's Daughter (1993)
47 King, Stephen : The Shining (1977)
48 Garcia Marquez, Gabriel : One Hundred Years of Solitude (1970)
49 Saint-Exupery, Antoine de : The Little Prince (1943)
50 Hughart, Barry : Bridge of Birds (1984)