3-4 teams? Maybe in the late 90's/early 2000's.
Even if the NBA will never resonate with the American public the same way the NFL does for obvious reasons, they've grown much closer over the last decade to replicating the general model. In a sport so dependent on stars and markets, there will never be as much parity as there is in the NFL. But, for all you can criticize Stern for, you better believe he had an enormous impact on growing the game globally, and, long-term, strengthening the talent pool to unprecedented levels.
If you don't like the NBA, that's understandable. I just can't quite grasp how one could watch the playoffs thus far - the Bobcats/Heat series notwithstanding - and conclude that the level of parity in the sport today isn't at an all-time high. I mean, there are plenty of stats that bare this out. We're a week and a half in and road teams are winning at a +.500 clip. The eighth seeded Atlanta Hawks just drubbed the Pacers in their own building to take a 3-2 series lead. The San Antonio Spurs - who just capped a dominant regular season - are knotted up at two with a team that had to play their way into the postseason in game 81. Not to mention, the Oklahoma City Thunder were about one minute away from trailing the Grizzlies 3-1. Conceivably, we could have a Memphis-Golden State/Dallas-Portland semi-final and nobody would be surprised. And when the bracket opens up like that, anything can happen - we, as UConn fans, should know better than anyone.