I like The Grudge 2 WAY better than The Grudge. I thought The Grudge was completely stupid and cheesy, like an exact copy of Ju-On only not scary... and then I saw the sequel. I actually cried a little out of fear XD it's pretty hard to scare me, so I really appreciated that movie. I made me happy. I recently bought it at a garage sale and rewatched it. Still scary.
So as far that fandom goes, for me it's just Ju-On and then The Grudge 2. The Grudge and Ju-On 2 were both pretty stupid. Don't remember how I feel about The Grudge 3 anymore. All I remember is that it reminded me of Silent Hill 4 a little too much.