The 90s were about Jordan dominating, I think slightly older fans see Magic/Bird in the 80s as the high water mark, older than that may point to the celts of cousy then russel, kids today may think Kobe followed by lebron was the peak
The 90s had a lot more to offer than just Jordan, though. An assortment of absurdly dominant centers, a Knicks team that was actually good, amazing stories (Dream Team, Hakeem winning two rings single-handedly, rivalries everywhere), and the beginnings of the Spurs and Lakers dynasties. I think the '00s were more characterized by guard play, the rising influence of European ball, and Spurs/Lakers dominance. Obviously there was still a lot to like, but it definitely didn't have the same casual appeal that the '90s did, at least not judging by the ratings. You may be right that people always see the era with which they group as the best one, of course.