I beg to differ. Anyone pointing out specific 2-3 year time periods misunderstand what I mean by Rivals. Sure there are teams that come and go, like the Jazz, now it seems that some consider the Thunder or even the Mavs. But, when you look at the history of the Spurs and Rockets since they have been in the NBA, there hasn't been another team over that entire history that you could consider a Rival of the Spurs. The 2nd closest would be the Lakers, but I don't think Laker fans would consider the Spurs to ever be their Rival.
Just because A&M or tu were in down cycles, and we were competing for championships against other teams during those periods, I doubt you would ever consider the other teams your Rival. It's the same with the Spurs - Rockets. Both fan bases have a strong dislike for each other and enjoy when the other team is struggling and get even hotter when they are both doing well. Hell, I've lived in Houston since '92 and Rockets fans have always hated the Spurs, even when there wasn't any particular playoff series or fight for playoff position. I know most of my Spurs friends back in SA still have a strong dislike of the Rockets, even when they are down.
This goes back decades, so if your in your 20's and early 30's, you weren't old enough to see the Spurs play Moses Malone, Calvin Murphy, John Lucas, Rick Barry, Mike Dunleavy, Sleepy Floyd, Vernon Maxwell, Rodney McCray, Mario Elie, Ralph Sampson, Kenny Smith, Otis Thorpe, Rudy T, etc. Nor were you likely to see James Silas, Larry Kenan, Johnny Moore, George Gervin, George Karl, Coby Dietrik, Alan Bristow, Mike Gale, Mark Olberding, Billy Paultz, Louie Dampier, Mike Mitchell, Artis Gilmore, Alvin Robertson, Willie Anderson, etc. The point being, this thing goes way, way back. It may have lost some luster during certain periods when one or the other was down, but there isn't another team in the NBA that the Spurs have this kind of history as a Rival.
AKA 13-0