Best
1. San Antonio - 1 less title than the Lakers, but far more relevance in non-title years (and no god awful teams)
2. Los Angeles - most titles and finals appearances
3. Miami - same titles, more finals appearances, longer period of relevance than Warriors
4. Golden State - last 4 years are the most dominant 4 year period since the 80's Lakers
5. Cleveland - the 5 Finals appearances (1 title) gives them the slight edge on a handful of teams just behind them (i.e. Boston, Detroit, Dallas, Houston)
Worst
This is way more difficult. I mean how do you compare the Kings and the Clippers. Both have 7 playoff appearances in the 00's, both have 3 1st round losses, but the Kings actually made the WCF, while the Clippers did not. Both were dregs of the conference for a long period of time, but the Kings have been awful for the last 11 years, so are they worse than the Clippers even though they advanced farther in the playoffs.
The Hornets seem to be the worst team, after that it is just a crap shoot but here is my attempt.
1. Charlotte
2. New York
3. New Orleans (though less years makes it more interesting)
4. Minnesota
5. LA Clippers (I give Sacto the slight edge on them b/c of the WCF trip and the 2 seasons of >70% win percentage)