I actually think the series is very mediocre, or at least the two most recent games since they're pretty different in comparison to Persona 1/2. Past the waifu simulator they're pretty average JRPGs with only their ballin art styles and good characters making it stick out. I'm still up to playing it once in a while, but it feels needlessly stretched out(not NEARLY as much as P3 though) and there isn't as much variety as I would like there to be. I also have my own complaints with the story and gameplay, but I guess I could see how people like it.
It's basically a Japanese version of Mass Effect with characters that don't suck.