Why has no movie version of I Am Legend dared to keep the original ending?

Question

The original book that led to the movies Last Man On Earth, The Omega Man and I Am Legend (and have I missed any?) has a somewhat pessimistic ending (Richard Matheson's great I Am Legend). I know that Hollywood often likes to sugar-coat stories as audiences often react badly to pessimism (e.g. the original cuts of Blade Runner, The Long Kiss Goodnight and many others).

But this is not a universal rule and some movies don't feel compelled to be upbeat (e.g. from two very different eras, Reservoir Dogs and The Parallax View).

So why not for I Am Legend? Has nobody ever attempted a pessimistic version? And what did Richard Matheson think of the movie adaptations?

Original ending:

In the book, the protagonist turns out to actually be The Legend, as opposed to the vampires of 'myth'. To this end, he suddenly realizes that he is the boogyman, a creature that walks by day and kills scores of the 'new population'. It transpires that the infected are actually starting to improve, so he allows himself to be caught and executed for his crimes - thus becoming the legend.

Answer 1

I'm going to have a go at answering all of your questions.

Firstly, I believe you have every adaptation listed above, with the exception of the trashy cash-in flick I am Omega, and perhaps, at a stretch, Romero's classic zombie films.

As far as I am aware, nobody has attempted an ending that echoes Matheson's original (and cerebral) conclusion to his novel, even though one might argue that the 2007 Will Smith vehicle didn't end with a classically 'happy ending' (although the ending they plumped for was far from satisfactory).

The simple reason for this is bums on seats. Movie making is a business, run by businessmen/women, and the dollar is the bottom line. Traditionally, the demographic that this kind of film is aimed at likes to see the (male) hero live to kick ass and kiss the girl - it's a brave (and rare) film that tries to break this mold. For the record, I think Darabont's take on The Mist is one of the greatest downers ever made.

As for Matheson's response to any of the films, I've dug around but haven't unearthed anything. Perhaps another user can dig a little deeper.