NES Era - Hydlide, anyone who has read my "Bottom RPG List" will know I consider this to be one of the worst RPGs ever made. Bad combat, terrible UI, absolutely no sense of direction and purposeful design. The game is a poster child of how not to make a fun game.
SNES/Genesis Era - This was actually a tough one for me because I kind of feel this was the beginning of the Golden Age for the genre so there are very few games I outright dislike for it. I may say one of the various D&D titles that was mostly text, menus, and stilted writing. The core gameplay worked if you were into D&D rules but I simply feel that console RPGs had streamlined the experience into something better so it was a bit odd playing something that tried way too hard to capture the "tabletop experience".
PS1 Era - Again, a bit difficult to find something because this is the end side of the Golden Age of console RPGs. I would probably say Revelations: Persona. While I don't necessarily have the outright anger against it like Fynn, the localization disaster for Persona 1 was unfortunate and the gameplay is a wonderful example of a critical failure in unique game design. I don't consider it unplayable, but the PSP port is significantly better with the exception of the music. It's definitely a "tolerate it or hate it" kind of experience though.
PS2 Era - I'm conflicted here, while there are some seriously sub-par games from this era like Star Ocean 3, Suikoden IV, and Xenosaga Episode 2; I can't help but gravitate towards an old stand by for a more specific reason. That would be Final Fantasy X. While it is not the worst game on the system, with the three previous mentioned titles all deserving said title for bad writing and crappy game design, I kind of want to nail FFX for popularizing several terrible game design choices that inadvertently killed many of my favorite franchises for trying to ape it. The fact it's design was taken as the core for what will be the worst game of next gen for me doesn't help. Linear dungeon design, challenge and core battle mechanics built around the end/post game, heavier emphasis on good looking cutscenes over writing and good pacing, a story that tells more than shows, pointless customization, a OST that takes a backseat to mediocre voice acting, disjointed world design, and overall just bland. While it works as an intro title for the series and genre, its ideas are far too calculated and inoffensive to be gripping, and the few good merits, either under perform or are saved for the end after you've lost interest. Again, while it's not the most offensive title of the generation, it's influence on other RPGs of the era made it difficult to really like the genre until the fad it created had passed. If I'm just going for a straight up bad game though, Xenosaga Episode 2 it is because it's mostly a game design predecessor for my next entry.
PS3 Era - Final Fantasy XIII, was it really a surprise? Of course not, I even recorded a crappy parody song to describe my dislike of this game. While there are certainly other games with worse writing and gameplay within the genre for this era, none of them had the financial backing to make them feel quite as insulting as XIII. Shameless pandering to FF nostalgia, brain dead dungeon design that looks pretty but lacks any substance to make it memorable, characters oozing with so much angst you could figuratively squeeze a Mexican Daytime Soap Opera out of them, a story that goes out of its way to strip away any meaningful themes the premise could have had, emotionally manipulative writing with zero substance, a mostly unlikable main cast with schizophrenic priorities, bad pacing in both story and game play, a mostly non-existent supporting cast, a cartoonish main villain, a literal deus ex machina ending that completely breaks the moral and theme of the story and would take two games later to actually make right, a gimmicky battle system that didn't work when Xenosaga Ep. 2 did it and they still found a way to strip away more tactical choices from the player, and the fact the main director threw a childish fit and blamed the fans for not liking it, despite all of its flaws that everyone else on the development team has the balls to be up front about, is the coup de grāce against this title. No AAA title has ever insulted my sensibilities as a writer or as an amateur game designer as much as this game has. It is to Final Fantasy what A.I. is to Steven Spielberg's directing career, a poorly conceived and manipulatively written affair that goes nowhere and ultimately does nothing but waste the audiences time.
Current Era - Much like the defining thread, I don't have an answer yet. While I've played a few RPGs on the current console generation, I feel it's too early to king "crappiest RPG". I feel like many of the games I have played are simply retreads of what was popular last generation so in a sense, I could say they are all underwhelming in their own way. I might say FFXV honestly for simply being a bit too basic for my taste and suffering from similar writing problems as XIII though it's less distasteful for me and I feel they at least made a likable core cast; but the game certainly never wowed me either beyond not being as much of a train wreck as I feel a game with its development history would lead you to believe. In some ways, it's like Duke Nukem Forever, where we were originally promised the moon and stars but instead settled for a fairly inoffensive but generic experience with the flavor of the franchise, though in DKF's case, I feel Duke's flavor of style has not aged well in the slightest. Course the console cycle is still young and I'm sure something worse will come from it. We do still have the VII Remake to dread/look forward to and Xenoblade 2 seems to have already disappointed everybody I know in some way. Hell, I'm still salty about Tokyo Mirage Sessions, so perhaps when I finally get around to playing that...