Whats a gaming failure or undeveloped project you wish had a more successful release/was fully realized? For me its tomb raider angel of darkness. There were a lot of problems with the production, ranging from lack of leadership to scrapped concepts to the unpreparedness of the team for the complexity of programming for the PS2. Core design didnt have enough time to iron out the kinks even with all the crunch time, and eidos didnt give them more time because they wanted to release in june.
The game was an unfinished mess, full of bugs and haphazard level design. But its gained something of a cult status within the raider community, with memes centering on its iconic side characters like janice the parisian sex worker as well as lara's feisty one-liners. Its still being kept alive by a dedicated community of speedrunners and unofficial remasters. I often think what could have been if it had more time to at least be passable at launch. Core planned two sequels that would have continued the story. Obviously they were scrapped, core design went defunct, and tomb raider was handed over to crystal dynamics.
If any of the 20 Harvest Moon sequels (the first one was '97!) had gotten their act together and seriously built out a full and complex universe (and released it for the PC), then the equivalent of Stardew Valley would've been made like ten years earlier and it wouldn't have been left up to some single developer to actually fully utilize the potential of that genre.
Imagine all the school holidays I would've lost, but also where farm-simulation games would be now. They basically stopped innovating after ~'03 until Stardew Valley in '16, so we had 13 years of ye dark ages.