Well,in my opinion, the list should be as follows, given my personal preferences...
1 Dan Simmons Hyperion 1989
2 Robert A Heinlein Starship Troopers 1959
3 Robert A Heinlein Stranger in a Strange Land 1961
4 Neal Stephenson Snow Crash 1992
5 George Orwell 1984 1949
6 Joe Haldeman The Forever War 1974
7 Ray Bradbury Fahrenheit 451 1954
8 Arthur C Clarke 2001: A Space Odyssey 1968
9 Aldous Huxley Brave New World 1932
10 H G Wells The Time Machine 1895
11 Orson Scott Card Ender's Game 1985
12 Frank Herbert Dune 1965
13 Isaac Asimov The Foundation Trilogy 1951
14 Douglas Adams Hitch Hiker's Guide to the Galaxy 1979
15 William Gibson Neuromancer 1984
16 Philip K Dick Do Androids Dream of Electric Sheep? 1968
17 Isaac Asimov I, Robot 1950
18 Larry Niven Ringworld 1970
19 Arthur C Clarke Rendezvous With Rama 1973
20 Arthur C Clarke Childhood's End 1954
21 Robert A Heinlein The Moon is a Harsh Mistress 1966
22 H G Wells The War of the Worlds 1898
23 Ray Bradbury The Martian Chronicles 1950
24 Kurt Vonnegut Slaughterhouse Five 1969
25 Ursula K Le Guin The Left Hand of Darkness 1969
Well, that's just my thought, anyway...eh,eh