I think the difference is that in the 8bit generation yhe majority of the game were bad relative to each other. The peak of the bell curve for 8bit was between mediocre to kinda bad games.
While there are more games in later generations, it feels like the console manufacturers took more control and regulated what was published. Bad games happen now because of shitty business decisions and bad story writing. You dont see garbage being published just because you can.
Back then i only had a few games but among all my friends we had a pretty good collection. As an adult playing on a retro console I've started to go through a lot of the games i never tried or didn't own and only played a few times.
While I'd say the total NES library is a majority of garbage games (publishers just figuring out how to make games, not how to make good games) I think the big thing i noticed is that the good 8bit games look and feel drastically different than the garbage ones. When you learn the history of the games then it makes sense.
The quality of the sprites, the extensive design of menus, transitions and other interactions, the storyline and dialogue. Even with only 8bits and crappy resolution the output for many of the good games actually looked and played well back then and even now. But I'd say about 90% of the NES catalog was garbage back then and still is now.