I think the mid 90's were a golden age of basketball, almost on par with what we are experiencing now. The 80's were probably third best, and the rest is whatever.
The NBA needs expansion teams for the league's popularity. They could handle 4-6 more teams right now, but will probably do Seattle and Mexico City first, then a couple down the road a few years.
The thing that would probably improve the popularity of the league is having some crappier players in the league due to more roster spots. Players will probably team up less of they can be the man on a team. That happens more of there are more teams. Let concentration of talent makes for more popular basketball, even though it's not as good. The good players look a lot better that way.