The movie could have been worse, but the original games had a much more intricate, thoughtful, cohesive, and original storyline.

*SPOILERS*

In Silent Hill 1, there was a cult that worshiped various fallen angels, and in a ritual to summon one of them, Samael, they were going to raise a human host containing Samael's essence. They found that he was too great, and so they had to use two hosts, twin girls, each one containing half of Samael. Lisa the nurse took one of them out of the city, and was killed by the cult when she returned. There, she was found by the Protagonist and his wife, who raised her, and surrounded her with love, which stunted the growth of Samael. The other girl was tortured and surrounded with pain to try and strengthen Samael, and ended up utilizing his power to transform Silent Hill into her nightmarish hell. Wifey died, and Harry or whatever decided to take Cheryl back to the city near where they found her. She wanders off, drawn to her twin, and the cult tries to rejoin the twins so that they can continue to incubate Samael. One of the endings has the girls being reunited, and then Samael being forcibly ejected prematurely, and weak enough to be defeated. The other ending just has you fight the twins melded into one being, and is exceedingly more difficult, as Samael is not exposed.

Silent Hill the movie had a girl (witch?) get burned by a witch burning cult because she was illegimately born, but it was interrupted and she didn't die. She went to a hospital, and she expelled her remaining decency into another baby, taken to an orphanage, and then transformed Silent Hill with her hatred. Cheryl's adopted mom took her to Silent Hill because she screamed it in a really corny fashion during a sleep walk.