The scares are cheap. A lot of the plot doesn't make sense. For example, we learn early on that both parents are unemployed. Yet somehow, they can still purchase a four bedroom home. Really? Clearly, the filmmakers were trying to take the film away from the original housing boom of the first Poltergeist and into our current post-recession world. This is not done in an effective way. I think you could also argue that certain aspects of post 9/11 culture are present. For example, the spirit world is saved by a small drone like toy. The family used it to see into the spirit world. There was also a much larger presence of technology used to monitor the dead. It all seemed a bit militant to me. Some sort of commentary on the current military industrial complex?
Another huge flaw is the constant use of CGI. The first film is so terrifying because the audience can't see the world that the dead inhabit. The family is terrified, because they don't know where their little girl is. But we see the computer rendered version here, completely eliminating any chance of suspense. I wish that Hollywood would figure out that the audience cares about more than graphics.
The film also took a weird turn with the young son. Somehow, it became a coming of age story for him. The parents are strangely absent in some scenes.
I gave this a 4/10, and in some ways I think I'm being a bit generous.