(CNN) -- If anyone's going to be the last man on Earth, then Will Smith seems like an ideal candidate.
Will Smith plays the survivor of a plague in "I Am Legend."
Cool and athletic, focused and unflappable, he's not someone who's going to give up on humanity just because the odds are stacked against him. Even at several billion to one, he's still adamant he can fix this thing.
A third movie version of Richard Matheson's classic sci-fi novel "I Am Legend" has been on the table at Warner Bros. for a long time. In the '90s, Arnold Schwarzenegger talked about following in the footsteps of Vincent Price and Charlton Heston (remember "The Omega Man"?).
Smith is such a different type, it's odd to think that he's taken over this mantle. In fact, he's scored consistently well in sci-fi, from "Independence Day" through "Men in Black" and "I, Robot," and there's no reason to suppose the tense, scary "I Am Legend" won't continue that impressive box office run, even if the movie itself flags on the last lap.
The opening couldn't be sharper. A television news report hails a medical breakthrough -- a viral cure for cancer, no less. Cut to New York three years later: abandoned cars, no one in sight, grass growing waist-high around Times Square. Something has gone very, very wrong.
Smith is Robert Neville. The cover of Time on his fridge door pictures a "Soldier. Scientist. Savior?" but that hanging question mark is well chosen, and we divine that his immunity is pure chance.
He's not quite alone. Neville patrols Fifth Avenue in his Mustang with Sam, a German Shepherd (also immune to the airborne virus), broadcasting into the void, then returning home to his Washington Square townhouse to put up the shutters before nightfall.
That's when the "Dark Seekers" venture out: feral, contaminated people with a rabid appetite for flesh but no pupil dilation reflex to protect them against sunlight.
By now, anyone who caught "28 Days Later" or last year's sequel "28 Weeks Later" may be experiencing deja vu -- in fact, if they called this movie "2.8 Years Later" it could pass as the third installment in the series with very little tweaking. Which is not to downplay the special frisson of seeing the Brooklyn Bridge ripped across the middle, for example.
Wisely dispensing with the Luddite rhetoric that bogged down "The Omega Man," "I Am Legend" doesn't have much time for Neville the soldier. While Chuck Heston dedicated himself to exterminating the albino hordes, Will Smith starts out firmly on the other end of the kill-or-cure scale.
At the same time, the film suggests his self-sufficient scientific rationalism is not enough. By day 1,001 he's on the point of suicide -- which is when the movie gets God in the comely intervention of born-again Alice Braga.
If the last half-hour feels thrown together, "Constantine" director Francis Lawrence mostly makes a virtue of the lean script, getting in and out quick, suppressing those inevitable nagging questions (are cockroaches immune?), always stressing Neville's solitary isolation.
So often, sci-fi is overproduced, but "I Am Legend" doesn't look like a CGI extravaganza. It looks like an edgy suspense movie shot on the fly in New York City after the fall. And because of that, it's all the more effective.