When someone is trying to show how awesome or awful a team is, a good tactic is to say "the Spurs have the NBA's best record since 2003" or "the Timberwolves have been the league's worst team since 2005." It puts consistent quality (or the lack thereof) in temporal perspective. And it can open some eyeballs.
Like, dangit Spurs, you are too good.
This chart uses cumulative win-loss percentage data since each year denoted. So a proper sentence using the table data would be: "Since [YEAR], [TEAM 1] has the NBA's best record and [TEAM 2] has the NBA's worst record." OR ... "[TEAM 1] has been the NBA's best team since [YEAR]. [TEAM 2] has been the worst."
The Spurs qualify as the "best team since" for every single year from 1987 on. If you go back to "since 1986," you finally get a replacement: the L.A. Lakers. Those two clubs are the only ones for which you can say they are the "best team since."
Best team since President Obama's inauguration? The Spurs. Best team since College Dropout? The Spurs. Best team since the debut of Mighty Morphin Power Rangers? The Spurs. Best team since the fall of the Berlin Wall? The Spurs.
Tony Parker Extended
Tony Parker Extended
Best team since Marvin Gaye's famous "Star-Spangled Banner" rendition? The Lakers. Best team since the original Shaft? The Lakers. Best team since Woodstock? The Lakers. Best team since the Cuban Missile Crisis? The Lakers. Best team since The Beatles formed in Liverpool? The Spurs.
The "worst teams since" have more variety ... until you get back to the late '80s, when the Clippers take over. The team's recent success can only paper over so much of the franchise's horrific history. You have to go back to the birth of the NBA itself — the ill-fated Waterloo (Iowa) Hawks — to find a franchise with a worse all-time record than the Clip Set.
About those Waterloo Hawks, by the way: they folded after one 19-43 season. According to Wikipedia, the Waterloo Hawks are the only Big Four team ever based in the state of Iowa. (And they are unrelated totally to the current Atlanta Hawks, who were founded as the Tri-Cities Hawks and played their earliest home game in Moline, Ill., before moving to Milwaukee, St. Louis and eventually Georgia.)
Two other early NBA franchises had worse records than the Waterloo Hawks and the Clippers, but they (the Denver Nuggets and Baltimore Bullets) were later reborn as ABA franchises under different ownership, so I didn't include them here. I also didn't include ABA records to keep things relatively clean. Thanks as always to Basketball-Reference.com for the data.