Ive seen, and own, all four.
Ju-On(V-Cinema)
Ju-On 2(V-Cinema)
Ju-On: The Grudge(Theatrical)
Ju-On: The Grudge 2(Theatrical)
Im a big Horror Movie Buff, and anyone who is, should check them out. While the story is simplistic, the way the films are shot in episodes that go from end to beginning(Think Memento), make it a fun experience. I find them downright creepy.