A few other films – not great ones – that were so different from the source that they might not be thought related.
**Ice Station Zebra
The Osterman Weekend
Force 10 from Navarone
Day of the Triffids** (except for the circa 1987 BBC version)
Invasion of the Saucermen and Invasion of the the Eye Creatures (believe it or not, actually based on a decent short story – “The Space Frame” by Manly Wade Wellman)
**This Island Earth
The Brain Eaters** (ripoff of Heinlein’s The Puppet Masters even worse than the adaptation of that name)
Arena not a movie, but the Star Trek episode “adapted” from Fredric Brown’s short story
Both the movie version of Pygmalion and the stage play and movie My Fair Lady, both of which changed the ending of Shaw’s play the same way.
Damned near anything by Edgar Allen Poe, including **The Murders in the Rue Morgue, The Raven, Pit and the Pendulum, ** etc.
Also just about anything by Jules Verne. Really. Most Verne adaptations are the pits. The decent films still made significant changes to the works (The silent 20,000 Leagues Under the SEa, the Disney version of it, the Mike Todd version of Around the World in 80 Days. I’m told that the Russian version of The Children of Captain Grant/In search of the Castaways is pretty good. The Disney version isn’t.)
Most adaptations of H.G. Wells. I except ** The Man Who Could Work Miracles**, which is really well done. And the original Invisible man wasn’t bad. But I’m not fond of George Pal’s versions of * war of the Worlds* or The Time Machine, or of any other versions of them. And the less said about most of the others Food of the Gods, Empire of the Ants, the better. Hallmark productions did an interesting TV three-part adaptation of several less-known Wells stories that was OK, but took significant liberties.
Most adaptations of H.P. Lovecraft, until recently. The last two decades have seen some pretty good versions of his stuff, but some awful stuiff, too.