The Omega Man starring Charlton Heston and the properly titled I Am Legend starring Will Smith. This version stars Vincent Price and is the most faithful to the book, not surprising considering Matheson helped write the script (though he wasn't happy with the results and used the pseudonym Logan Swanson).
This version is the only one to truly convey the original theme of the novel: in a world where there is only one human and everyone else have become vampires, the natural and supernatural have switched places. Man is the creature of the shadows, the boogeyman of lore that frightens the undead majority. While in the book, protagonist Robert Neville accepts this realization with a quiet sadness, a lament over the passing age of humanity, Robert Morgan of the movie rebels against this, defiant to the end against the "freaks" and "mutations," not realizing by default he's the freak and mutant.
Price is an unusual choice, to say the least, for the role of Morgan, a normal man being crushed by the weight of extreme loneliness and despair. His style often lent itself perfectly to suave villains and mad scientists. It takes a little getting used to, but Price plays the role admirably, treating his task as a vampire hunter not as a joyous Van Helsing but as a tired, worn-down man filling time more than anything else. The loss of his family, the drudgery of his routine, the overwhelming sense of isolation, Price plays it seriously. It's not campy or fun as we normally expect from him, but it gets the job done.
The movie also includes several neat details about Morgan's life and how he gets by, including a machine for sharpening stakes, a generator in his garage, and the maps marking all the buildings he's investigated for vampire lairs. After the vampires destroy his car, Morgan amusingly goes to a dealership and takes a station wagon instead of a corvette because it's the closest to a hearse he can find and he needs it to haul bodies. It'd be nice if we didn't have so much voiceover by Morgan explaining we he's doing, but then, I imagine, most people would complain the movie's too quiet.
But - there's always a but - this is still not the sublime I Am Legend horror fans deserve. Yes, Price carries the movie admirably, and there are nice visuals, but overall, it's a cheaply made, rushed through production. The vampires in this movie don't even seem to have fangs and only stumble around in half motion like a bunch a drunks afraid to move lest they fail a sobriety test. The action scenes of Morgan knocking them over are laughably tame, even by the standards of 1964.
The movie also makes some weird pacing decisions. Naturally, we get some flashbacks back before the vampire plague hit town, but we didn't need it in a twenty-minute block in the middle of the movie. Occasional fragments referred to throughout the film might have kept things interesting, but by loading the flashbacks into one section, the filmmakers completely kill the narrative's momentum. The movie also rushes through key passages in the book - finding and catching the dog, the encounter with Ruth, etc. - so some of the power is dissipated. The movie doesn't even reach ninety minutes; it could have used more time to space things out and support them.
Vincent Price fans will do well to check out The Last Man on Earth, and those interested in the evolution of movies about the end of the world will find much to enjoy. It's just a shame the story is told in a mostly drab, flat way. I still hope for a truly stellar adaptation of Matheson's work, but last I heard, the plan is to do a prequel to the Will Smith version. Ugh.