The third time's the charm, right? I mean the Will Smith vehicle I Am Legend has the same title as Richard Matheson's classic story so right there it has to be ahead of the previous two times that that it's been adapted for the screen. For the first two thirds I could could have believed that but it all fell apart in a terrible third act that undermined the entire film for me.
A disease has killed off nearly everyone on earth turning the vast majority of the survivors into what are essentially vampires (they burn in sunlight, are attracted to blood, and have a certain amount of superhuman physical abilities). Almost anyone who is naturally immune has been torn to pieces in the initial chaos of the disease but Robert Neville who was working on a cure has managed to survive on the island of Manhattan. Neville struggles to survive each day in isolation while continuing to hope for the creation of a cure. He occasionally captures one of the sick people to use in his research. His problems really begin when one of the vampires starts aggressively pursuing him.
And here is where the film really diverges from the original story. When I say diverge I don't mean things like "changed California to New York" or "altered the nature of the virus"; there are minor things done for the sake of adaptation and they don't hurt the core themes. Matheson's story takes this rather generic set up and adds a particularly subversive plot twist that changes everything (if you haven't read "I Am Legend" then it's well worth your effort to get it and read it). The film appears to be building to this plot twist but then abandons that developing thread completely. You can almost see in the script the marks where it was abruptly cut off and pulled out. What it was replaced with was the same generic formula that Matheson was subverting.
Will Smith does a fine job as Neville conveying the wide range of emotions of a man who is close to dying of loneliness. His only companion is his dog and talking to it or himself provides the bulk of the dialog in the film. There are brief flashbacks to the early days of the infection that help give us some context for his tragedy and Smith is very convincing with his mental breakdowns.
The film acts a bit like a guided tour of Manhattan as Neville's actions are inevitably backdropped by some famous location that has fallen into ruins. The location CGI work is impressive and most of it feels very real.
There is a problem with the CGI for other things, unfortunately. The only real animal in the film is Neville's dog but there are CGI deer, lions, birds, and vampiric dogs that are very unconvincing. The worse problem is the CGI vampires; by chosing to not use any real people for the vampires the filmmakers took something that should have been simple and effective and completely undermined it. Extras in make up would have been a much better choice.
I'm going to spoil things just a little now but it's a situation where I think they're already spoiled. The film ends on a literal deus ex machina. The only way that things could have been worse is if they had actors portraying the Greek gods lowered into frame to fix everything. As it stands the Judea-Christian God gets to do it but fails to put in an on screen appearance. I Am Legend was such a bleak, depressing movie that it could have used Matheson's subversive plot twist as one final gut punch to go out on. Having God make things better is bad writing, a disgrace to the original story, and not even particularly interesting. At least in The Stand God actually appears on stage, in I Am Legend the filmmakers just beat you over the head with the fact that God made things better.
Despite that incredibly terrible ending I still think the first two thirds were good and for that reason I'd say it was worth watching on video but not paying to see it in a theater.