Knowing that readers of the original book and viewer of the other films that was based on the book, The Last Man on Earth and Omega Man, I think this version of I Am Legend is worth watching.
The movie starts with a news section that reports that cancer has been cured. The only draw back is found a couple months later that 9% of the people that took the cure turned into vampire/zombies that ended up killing most of the 91% that was left and now only one man is left. And Will Smith's character Robert Neville is that man.
Thinking he is the last man not infected by the virus, Neville and his only companion a dog Sam, goes day and night in New York trying to survive and also tries to find a cure to the virus. The movie some times switches between flashbacks to when the outbreak started with his family trying to get out of New York which slowly is revealed what happens to them.
Acting of part of Will Smith was pretty good compared to the rest of his films and is on par to his role in iRobot.
The only draw back to this movie is toward the end when someone else is brought in and really brings down the feel of the movie.
Now I don't care what Prelude says, it didn't feel like it was pushing ads in my face and I found I Am Legend a good film and really enjoyable.