Voice is great because it have very strong thriller/suspense style. Voice distinguish itself from other police procedural drama, other police procedural drama have a mystery style. The standard formula of police procedural drama: there is a case, police investigate the case and find clues after clues, and finally they close in on the culprit. But voice is very different, a crime happens, and police have very limited time to solve the crime or the victim will die. Because of the strong urgency to solve within a time limit, this create a very strong thriller/suspense emotion in audience.
Voice is the most original police procedural drama that I've ever seen. All other police procedural are mystery, and voice is thriller/suspense.