This was actually film was a good idea ("The Entity" meets "Disturbia"), but got spoiled by three things.
(1) Lou (the dead cops's partner) is a moron; "you didn't have to kill him... ok, it's taken me 5 years to look into your case, and you were right, he was beating on you, but you didn't have to kill him... oh look an evil ghost, can I talk to it?" Die and die now you one-dimensional idiot.
(2) Serious plot hole - if the ring sets the ghost free, why didn't it free him during the sink scene?
(3) The big reveal of the ghost was made far too early - they should have left if for the end to keep everyone guess whether Marnie was crazy, really had someone else kill her husband, or if the house was haunted.
Now that said, there was some nice touches. The blood reappearing on the wall was great. The sense of loneliness in a crowded community (Halloween etc) was just fantastic. And the fight scene between the ghost and Joey was awesome - I loved that. The CGI was reasonable, and it was good see Famke Janssen not playing Jean Grey or Onatop.
Honestly, I wanted to love this movie, but although the flaws were few, they were so major that made me go "oh for crying out loud" too many times