You talk about "I am legend" with Will Smith. This film was horrible. I tell you why. Its based on a science fiction book from 1954, written by Richard Matheson (you should take a look).
Moskitos brought a desease and infected all humans that died and got reborn as vampires. Only Robert Neville is alive and gathers food and candles in daylight. Later he meets an female person that isnt infected. At the end of the book he finds out that she is infected too and got terrible woundet inside a combat with the vampires. He is watching out of his window and realises that a new society of vampires has the rights for existence and that he - the only living human - is now the monster that has no place in this new world anymore. He kills himself with a pille and his last words are: "I am legend"
You see the difference? In the end of the movie Robert dies and the woman saves the world because she holds the antidot inside her bodie. You cant have leaving your audience without giving them a happy end inside a hollywood movie. I suggest you to watch the movie "I am omega" that was released in the same week. Its a much better movie based on the book than this hollywood shit.
Yeh, I read up on that film as well before I saw it.
I'm not sure if this was from the book or some other film re-make of it but he went out and killed the vampires every night. They were scared of him and (as you said) he was seen as the monster and the legend in fairy tales just like we are scared of vampires killing us and are told stories of them. The vampires and him have switched places.
I still thought the film was very good though, whether or not it was based on the original or not, it was still a well-made film.