999 was an extremely solid story with a legendary final twist.
VLR, my GOAT before playing ZTD, was legendary every step of the way. Quark, Clover and Alice were underwhelming, but the remainder of the cast was incredible. The story had even more twists and turns, and the central mechanic (the Prisoner's Dilemma) still makes VLR have my favorite premise not just in video games, but all fiction. Its OST was in a different, more ambient style, but it worked exceedingly well. The art style was shit, admittedly.
The plot did have a few stretches here and there, but made up for that by being extremely compelling. It took the first game's idea of the Morphogenetic Field and developed on it in an exciting way. The last third of the game (Luna END, bomb and lock shenanigans, those last two hours!) is the stuff of legends.
It built on 999 in every way without recontextualizing its most touching moments (which is a good thing, because 999 didn't need that).
It's a perfect sequel. It perfectly explained the events of Rhizome-9 and really upped the stakes for what was to come.
Zero Time Dilemma shat utterly and completely on the series. I actually like the idea of the game doing a 180 on its previous messages and themes. That's not the issue I have with it. What issue do I have with it?
1. It's not a VN anymore. Cutscenes don't cut it with a series as complicated as Zero Escape.
2. The graphics. Unholy hell, the fucking graphics. Sock puppets have a decent chance of being better at conveying the emotions of the characters than whatever the hell ZTD was trying to pull with 20 hours of 3D animation on a (probably) shoestring budget.
3. The setting is really, really bland. The game was supposedly taking place at a test site, but they went and changed the setting to a bomb shelter instead of Dcom ten minutes into the game.
4. It reuses music from the first two games like crazy. Besides the puzzle rooms, more than half of the music you hear is from the previous games (and with nowhere near the same emotional impact, Blue Bird Lamentation is the sort of thing you use sparingly and not fifteen bloody times). Which is a real damn shame, the new compositions for ZTD are actually really, REALLY good (can't recall a single scene with it, but Ustulate Pathos-Vintage- is wonderful).
5. It is heavily dependent on VLR (we know who five of the people there are). Even so, it handwaves the plot points from VLR and tries to become its own thing, and fails miserably. Eric, Mira and Q bicker among themselves more than Radical-6 and Free The Soul's screentime, combined. Radical-6 is just some random lab-grown virus. The whole FtS subplot is almost literally resolved by Delta going "Oh, by the way, I'm Brother." VLR's hanging plot threads were practically the sole reason people anticipated ZTD so greatly, and they end up being trivialties in the end.
6. ZTD tries to provide a counterexample to VLR and 999's message that the right thing to do is to use the morphogenetic field or to SHIFT, yes- that's actually a really cool idea from the outset. However, we don't see the characters reflect on this at all. Junpei's main objective is proposing to Akane, who herself is characterized horribly here. Phi's absent for much of the game. Sigma knows much about genetics, cloning and AI, and is yet nothing but a belligerent idiot as the events unfold. If Akane somehow never considered and resolved the fact that there are infinite timelines in her whole life, even then we see absolutely NOTHING about how this reflects on her (or Sigma). The message just comes off as ZTD being edgy for edginess' sake. Hell, the cast could've even come to terms with it and decided to seek some other objective or meaning in life. Leaving the ending ambiguous about what finally happens does not excuse this, because it portrays the game's main assertion (that there's no meaning or morality in SHIFTing) as irrelevant and uninteresting- an ambiguous *ending* is a good idea, but we barely see any self-reflection whatsoever.
7. The central mechanics, Fragments and Teams, are utterly trash. The nature of the Fragments impede practically any character development. While the idea of having to start over from zero every time you wake up is compelling, it just doesn't go anywhere. There are a few interesting scenarios (Akane finding Junpei's head comes to mind) but the way it's used really doesn't convey the sense of pointlessness the mechanic tries to convey. This is where the Team system comes in and shits the bed SPECTACULARLY. The Team system limits character interactions to three situations at the beginning of every fragment: Eric gets mad at Q, Sigma and Phi argue, or Junpei acts like a little shit. They get played out extremely quickly. If the teams kept switching, we could have had far more interesting situations- Sigma getting angry at Eric for freaking out for example, or Diana calming Q down. The lack of character development, combined with the repetition in character interactions, really made the first 2/3 of the game rather boring.
8. The ending is cringe-worthy. In connection with #6, the only solid response our characters give to Delta and his revelations (if you can call them that) is to scream about the power of hope and friendship in his face. A morally ambiguous ending is a good idea, but not a good idea for a game meant to be the long-awaited finale of a trilogy to come up with an ambiguous new antagonist and leave it at that.
9. Delta and everything about him. "Terrorist kills eight million so I killed six billion" is really too abrupt and contrived. Even more contrived is how he holds the Decision Game so that he can exist. Delta speaks as if he has the moral high ground but he tortures the cast over and over for his own gain (we never get the feeling that he does that solely-or mainly- to create Radical-6). The game tries to say that SHIFTing to try to save the world (after Sigma and Akane literally devote their lives to this purpose) has no meaning, but Delta (the person with supposedly different moral viewpoints on SHIFTing) does the exact same. I suppose it supports the "There is no morality" argument, but the game fails to make that argument feel heavy or important. It tries to paint a poignant picture that everything is pointless but ends up merely undoing whatever emotional and plot-related buildup ZTD and the series as a whole had. In other words, the game's trying to switch gears to nihilism and cynicism, but attempts it so superficially that it merely disappoints the emotional investment we had in the series.
10. The sex scene (and the "rape attempt"). This is more of a nitpick, but the game sure does portray a weird image of consent and uses rape as a superficial plot device. I can almost excuse the Diana scene (besides the alcohol, it IS a scenario where Sigma's trying to calm her down and ensure her safety, I didn't get the impression that he wished to abuse Diana). I disagree with the concerns about age, though.
The rape scene was a risky move and besides being bad writing, it really distressed some players too (for obvious reasons).