While (from what i've seen), the fanbase is very passionate about the games, the games have recieved mixed to poor reviews critically, at least here in the West (don't know any sales numbers but it must be doing decently enough to have four main games, three of which have remakes, and a bunch of spin-offs). Long story short, all the critics pan the series for being way too anime and also the fanservice (which i guess is a valid complaint). And that's one of the reasons i love the series (though it's not the main reason). I love how self-aware it is and how it makes fun of both video game and anime tropes. One sidequest in Hyperdimension Neptunia Rebirth 3 makes fun of Indiana Jones and the Kingdom of the Crystal Skull and that's hilarious. While the stories themselves are pretty dumb, the true highlight is the amazing characters and their wacky dialouge. Every character is some sort of trope and they all make fun of each other for it. My favorite story has to be from Mk2/Rebirth 2, where it's essentially a war on game piracy and emulation. And because of stuff like this, very rarely do the stories take itself seriously, which is why it's so great.
The gameplay is pretty mindless at first but it gets really fun and while the soundtrack ranges from average to good, the OPs are really good.
My only complaint with the series, at least with the Rebirth trilogy, is that dungeon design is extremely lazy. Oh and manipulating Shares to get the true ending (or any other ending) can be a pain but that's really only an issue in Mk2/Rebirth 2, where there's 9 endings and i only care about the true ending anyway. Also the English voice acting being too normal and quiet. Japanese voices fit the characters way more.
Hyperdimension Neptunia is one giant meme and i love it. So much so that it ranks 3rd on my favorite JRPG series list and 6th on my favroite video game series list. I never not have a fun time playing these games (mostly) and I look forward to Super Neptunia RPG releasing on the Switch next year.
Xenosaga Episode II: Jenseits von Gut und Böse
Considered to be the worst game in the Xeno series by many fans....and i don't really get why. Yes, battles can drag on. Yes, it killed the original plans for Xenosaga but that can be blamed on Namco's interference (Namco removed series creator Tetsuya Takahashi from his own project, for some reason), yes Takahashi actually had to remake the game to fix it (and this version only released in Japan on the DS). Yes, it sold like shit (and the trilogy in general underpreformed commercially). But honestly, i found it to be a better game than Xenosaga Episode I. Not that Episode I is bad by any means, i just personally consider it to be the weakest Xeno game.
Episode II fixed a lot of Episode I's flaws for me. Combat is better, music actually exists (Episode I barely had music and while it did have the amazing Albedo's theme as well as the two beauitful ending songs, most of the game's soundtrack was just slience, Mitsuda why) and the story isn't an glorified prolouge. It also kept what made Xenosaga Episode I good. Good characters, the philosiphy and Albedo. Albedo is amazing, best villain in the Xenosaga trilogy and fourth best villain in the overall Xeno series.
Episode II is on the lower end of the Xeno ranking for me but it's not the worst game in the series like many fans say it is.