“American Exorcist” (*1/2 out of four) was a congenitally derivative horror show about a paranormal investigator (Falon Joslyn) who becomes trapped in a haunted skyscraper on Christmas Eve and is confronted with supernatural and religious forces unlike any she has investigated before, which all may tie back to (what else?) a mysterious priest (Bill Moseley). Gonzo opening involving a shootout at an office grabs your attention but this has virtually nothing to do with the rest of the story which soon becomes predictable and boring. Moseley is good in an unusual role for him but that doesn’t mean he shouldn’t be waiting for Rob Zombie’s phone call for “The Devil’s Rejects 2.”