I know lots of people on Amazon haven't been impressed by this film, and they've a right to their opinions. I guess it's just people like me who enjoyed it.
I love and hate this film. I hate it because it still gives me nightmares sometimes (I have a phobia of aliens, started in childhood by ET...), but I love it because it tells a beautiful story with the concept of an alien invasion as a chilling backdrop. A man who loses his faith after his wife is killed in a freak accident, then finds it again after (through perhaps fate) his son's life is saved.
I found the aliens terrifying-that first time when Graham (Mel Gibson) looks out the window and sees one in the dark is one of my scariest movie moments ever.
It also has a beautiful and often chilling score by James Newton Howard. I had to buy it. Look out for the amazing music during the climax.