If it's fictional I tend to not worry, but if it's related to a historical event it's more troubling.
I've heard "The Last Samurai" is not very realistic for example.
Other than that, if a movie is based on a book and they get some major detail wrong, that can be an issue also. Example: The "I Am Legend" movie ending completely changed the meaning of the whole work IMO
I agree wholeheartedly. I'm also having one of those "don't get me started" moments. The original Richard Matheson novel I Am Legend is a big obsession of mine, I even have an original 1954 edition, and several other editions, I'm just that sick.
The Will Smith version had two endings, and there's elements of both which only faintly resemble what the book was going for. Without getting into spoilers, I'm not sure which one you saw- either the "happy" one or the more "sad" one? Either way I was surprised by one which had a thread of loyalty to the novel, though minor, but both endings still fell short.
Not to mention the producers wanted to deviate too far from the novel: Neville is no longer the last man on Earth, because it's Hollywood and they have to give him a love interest, and they can't make the story out to be TOO hopeless.
Changing the setting from LA to New York is not that big of a deal, but you could use New York for any other movie, and still make a convincing dystopia from an abandoned LA.
And like in the Omega Man, Neville's a high ranking Army scientist, not an average joe plant worker like he is in the novel.
The Will Smith movie is actually the third adaptation (Last Man on Earth with Vincent Price was closer to the novel, and later came Omega Man with Charlton Heston. (Technically, Night of the Living Dead was loosely based on the novel, Romero himself admitted this in several interviews). I actually still appreciate all versions as wonky, bastard children of the original.
In the 90's, Ridley Scott attempted to do a version with Arnold Schwarzenegger (immediately after WB's Superman movie tanked), and it was really ambitious. Two different scripts, and Hollywood wanted the one that sucked (Arnie fights the villain, who falls to his death, and Arnold and his new girlfriend ride off into the sunset on a tugboat as he voice overs the words "I Am Legend"). One reason WB frowned on this project was not just the high budget but because Arnold had just came off of a big box office failure, Batman and Robin.
Guess who wrote Batman and Robin? Akiva Goldsman. Guess who produced and co-wrote I Am Legend? Akiva Goldsman! Other screenwriters credited on I Am Legend included Mark Protosevich, the writer of the original bad script for the Arnold version that Ridley did not want to use, and the husband and wife team that wrote Omega Man. Those names appear before Goldsman's on the credits, who basically took those scripts and didn't stray too far from them. The one thing I did like about Protosevich's script was Neville using vials of his blood as bait, that was clever.
Final takeaway is this: Warner Bros has never wanted to do a loyal I Am Legend movie, they have only wanted to remake the Omega Man. I believe a faithful version of the novel could still be pulled off.