'I Am Legend' was a decent survival flick, but the stuff that was really great was undercut by terrible CGI vampire monsters and an ending that didnt hew close to Richard Matheson's original story.
In the original ending for the film, it turns out that Will Smith's character has found a cure, so he tucks his fellow survivor and her son away in a coal chute with a vial of blood from his test subject in hopes that they will finally make it to the fabled survivors' colony. Then he charges the group of mutant vamps with a grenade, sacrificing himself so that his cure may live on. But in this alternate ending, which is more like the story on which the film is based, Smith lets the vamps in and offers up his test subject to their leader as an apology. In a touching moment that shows that these monsters are still human, they accept and leave Smith and his new friends to go on with their lives — so they do, embarking on a journey to find the colony. It's still a little silly thanks to all the CGI, but we think it's a more interesting — albeit subdued — ending.