It's just not an accurate comparison. If you want "parity" in the NBA, you'd have to change it to a 30 game season with 1 game series in playoffs.
This wouldn't help anything. Right now teams are about 19 to 21 games into the season. You've got a large enough sample size that most teams are going to finish the season with a similar winning percentage. Playing less games doesn't improve parity, evening the talent does.
In the NBA, elite teams have either been stacked with talent or managed really well. In a case like San Antonio, they have have aging stars but have also been managed really well. OKC got lucky in the draft and lucky to have a superstar that isnt forcing himself to a big market. The Knicks and Heat are destination cities. The Lakers stacked the deck and still stink but they should improve. OKC and San Antonio are the exception to the rule because they found some of the few superstar players that don't need the big market to be happy. Every year Boston, LA, Miami, Dallas, Chicago are up toward the top because stars want to go there. NY should have been better but they've been managed terribly over the last 15 years.
There might be a bit more parity in the NFL but it is also lopsided but instead of being driven by superstars stacking the deck, it is driven by elite QBs most of the time. Teams like Green Bay, New England, Denver, and NYG are Super Bowl Favorites based on their elite QBs.
The big difference to me is that when you look at the elite teams in the NFL, the small markets actually have a chance. Green Bay, Denver, Houston, Baltimore, San Francisco, and Atlanta are in the top 8 in the NFL. Those would not be destination cities in the NBA. If one of those cities did well in the NBA there is a good chance that they would have a short run as their superstars would try to leave for NY, LA, Chicago, Boston, Miami, or Dallas. Teams like NY who have found a way to lose despite their advantages have been pathetic for management reasons.
The deck is so stacked against small markets in the NBA that it gets frustrating to watch as teams like Orlando and New Orleans are not going to keep their stars usually. You get far fewer examples of guys like Eli Manning in the NFL forcing themselves into bigger markets. The NFL sells their product and gets amazing ratings, the NBA depends on big market teams doing well or ratings stink much like baseball.