I agree with you that many adaptations have sucked. However, here are some that worked, at least for me:
The Day the Earth Stood Still (1951) (Harry Bates' Farewell to the Master): **** - even though it was outright pro-United Nations and Soviet-friendly propaganda.
The Thing From Another World (1951) (John W. Campbell Jr's Who Goes There?): ***1/2 - John Carpenter's 1982 remake, The Thing: ** - even though it was closer to the original story.
When Worlds Collide (1951) (Edwin Balmer and Philip Wylie): ***
The War of the Worlds (1953) (H. G. Wells): ***1/2 - but still looking forward to the Spielberg remake.
This Island Earth (1955)(Raymond F. Jones): ***
Invasion of the Body Snatchers (1956)(Jack Finney's The Body Snatchers): ***1/2, 1978 version: ***, 1993 version (Body Snatchers): **
Forbidden Planet (1956) (Shakespeare's The Tempest): ****
The Incredible Shrinking Man (1957) (Richard Matheson's The Shrinking Man): ***1/2
The Time Machine (1960) (H. G. Wells): ***, 2002 version: **
Village of the Damned (1960) (John Wyndham's The Midwich Cuckoos): ***1/2, John Carpenter's 1995 version: **1/2
The Power (1968) (Frank M. Robinson): *** - but still deserves a remake!
Planet of the Apes (1968) (Pierre Boulle): ***, 2001 version: **
There are probably some others that I've forgotten.
Great list, and I agree on most of them! Unfortunately, not one there is less than 37 years old, most nearer 50!
Today, in Hollywood, there is very little chance of getting a fair reading of a script withouth most of it being too 'controversial' for today's PC world.
When Tom Clancy has to rewrite Sum of All Fears, and '24' is vilified for having the audacity to look like real life in it' schoice of bad guys, there is zero hope that John Ringo and Eric Flint would get a reasonable chance.
Hate it, because both Flint's 1632 univerese, and Ringo's Posleen wars deserve a good series of movies.
Going back to reading "Ring of Fire" now, and have Vol IV of the "Grantville Gazette" waiting.... :)