For the past 13 years, ESPN has reached out to sports fans asking them to rate their favorite teams, considering things from championships and team success to ticket costs. ESPN uses the feedback to rank every franchise in pro sports; all 122 of them. They call it the "Ultimate Standings".
The Spurs, who have finished in the top ten every year since 2010, earned the top spot in the 2015 ultimate standings for the second time in three years. As one of the most respected franchises in all of sports, It's no surprise that the team finished number one in players, fan relations, coaching and ownership.
An NBA team has now finished first for four years in a row (Spurs in 2013 and 2015, Memphis Grizzlies in 2014, and Oklahoma City Thunder in 2012). The Grizzlies finished second overall due to their consistent team success and financial efficiency, with the Thunder finishing seventh. You can see where the rest of the NBA finished here, and where all 122 pro teams ranked here.
I highly recommend checking out the stories tied with the Spurs' ranking; a Q&A with Manu Ginobili, a Jackie MacMullan column on Coach Pop, and an interesting story from Michael C. Wright on a local Spurs fan.
This is all thanks to the undying loyalty of you, Spurs fans, so keep it up.