The film opens in 2012 in a post-apocalyptic New York City, with Robert Neville (Smith) believing he's the only uninfected person left alive. He spends his days much like you and me: working out, watching DVDs, and testing vaccines on ravenous zombies in his basement laboratory. Occasionally, he hunts deer in Times Square. While the light-sensitive, zombie-like infected roam the streets at night, he cuddles up and snoozes with his dog, Sam. But mostly, he emotes.
We flash back to his memories of the outbreak and see Neville's frantic attempt to evacuate his wife (Salli Richardson) and daughter (Smith's daughter, Willow), with tragic consequences. If thinking about that every day isn't bad enough, he has to put Sam down, Old Yeller-style, when she's infected in a trap set by the smarter-than-they-seem infected.
This sends Neville over the brink, and he ceases to care whether he lives or dies. That is, until he finds a pair of kindred, uninfected spirits in Anna (Alice Braga) and her son Ethan (Charlie Tahan). The two try to convince Neville that there's a promised land for the uninfected up north in Vermont. But Neville remains dubious and feels it's his duty to stay at "ground zero" to continue his efforts to develop a cure. The decision to stay or go, though, is about to be made for him when the infected discover where he lives.
The End Product
I'm all for using computer graphics to create the sort of stunning landscapes seen in I Am Legend: the familiar New York skyline hauntingly silent, with desolate streets cluttered with abandoned vehicles and overrun by savanna-like grass (Although really, is there so much upkeep involved in preventing grass from growing over pavement that the streets would turn into wheat fields with three years of neglect?).
However, we live in an age of digital laziness where movie directors like Francis Lawrence can't be bothered to work with real-life actors in order to achieve an organic sense of realism. The gritty authenticity of makeup and blood squibs has been replaced by the sterile artificiality of computer graphics. That Lawrence actually started out using live actors for the infected in I Am Legend and decided that computerized ones would work better makes his sins all the more egregious. If he didn't know how to make real people in zombie makeup look and act scary enough, he should've re-watched 28 Days Later or the Dawn of the Dead remake. Or stick to music videos; whichever works for him.
Presumably, Lawrence fell in love with computer effects on his debut, Constantine, but while that film revolved around demons and netherworld creatures, there are no supernatural elements in I Am Legend. The crux of this film's power lies in human emotion and the grounded realism of what a post-apocalyptic world might look and feel like. By populating this world with creatures out of The Mummy, the director commits the cardinal sin of moviemaking: he jolts you out of the film's universe and draws attention to the fact that you're sitting there staring at a flat screen.
Apart from the zombies, everything else in I Am Legend is at least competent. Smith is likeable as always and delivers moments of emotional torment that cut to the bone. Script-wise, the movie blends elements from the Richard Matheson book and Charlton Heston's Omega Man. It has its own modern spin, of course, and remains engaging throughout -- albeit mostly due to Smith and the setting.
Because of the way the film is structured (something borrowed from the source material), the bulk of the action takes place in the second half, making that portion feel rushed and underdeveloped before crashing headlong into a silly, overwrought ending. Even if it had to deviate from the book, the movie would benefit from a longer, more fleshed-out confrontation between Smith and the infected -- particularly in light of the elements of humanity the film portrays, and subsequently abandons, in the latter.
Even without the computerized baddies, I Am Legend wouldn't necessarily be a great movie, but it would be a lot more enjoyable, and it might well reach the terrifying depths that the material suggests.