Personally, I think BB is both overrated and under-appreciated at the same time. Allow me to explain my train of thought:
BB came out at a time when adult games were still in their infancy, so there was not a lot of variation back then, hence a lot of players flocked to BB, which was admittedly one of the best games around at the time. Still, aside from the (still) very nicely done graphics, there were a LOT of issues with the game.
The characters were mostly selfish and/or unlikeable (the player character himself is one of the biggest assholes in all adult games), the story made no sense (why exactly DID they get that house and how the hell did nobody ever find out about the 24/7 livestreams of their entire lives? In this day and age, someone would be bound to find out, some way, somehow), and the grind was absolutely atrocious. Heck, even the greatest aspect of the game, the amazing renders, also had weaknesses on their own, with a lack of animations (not that it bothered me, since I am not one of the people who MUST have animations in my games) and a tendency to make obstructed view points of the sex scenes (in most scenes, Dark Silver finds a way to have an arm/leg or whatever blocking the view of the dick entering the pussy. Its almost as if he is scared that he will become gay if stuff like that is shown).
When looking at these points, the game is overrated, which is agreed upon by many players. However, many of these people also seem to forget that BB inspired many people to try and make their own games, and helped push the (western) adult gaming market along, when it was still trying to find its footing. Despite how many awful clones and rip-offs the game spawned, it also inspired some people to make games that were actually good, even if they were doing it, just to prove that they could make a game that was superior to BB. In this regard, the game is under-appreciated, because it did a lot of good for the industry, even if certain people seem eager to forget that.
BB is Ronda Rousey. She showed up at UFC when she was needed, she dominated everything she touched and inspired a lot of people to become better. Then she got her ass whooped, by fighters who were simply superior to her in every way, but still wouldn't even be there if it weren't for her paving the way for them. Now the UFC is dominated by fighters who are arguably superior to Ronda, but she is still owed a great debt for pushing the industry along. Just like BB pushed the adult games industry along.
BB was a giant, a necessary player when it was needed, but now is outclassed in almost every way by newer, better games. It should be praised for what it accomplished, but not foolishly regarded as a flawless miracle either. BB is both terrible and great, and if nothing else, I personally think it deserved to have a completed ending, instead of the rushed mess we ended up with, but I have no interest in it any longer, and certainly no interest in all these clones that are still springing up all over the place.
TL;DR: BB is far from perfect, but did a lot of good things for the adult games market. Now it should be left alone and people should turn their sights forward.