The Catalan admitted that Los Blancos' triumphs, particularly in the Champions League, deserve praise.
"They're a very strong team, in every way, and they have helped me be a better coach," Guardiola told DAZN.
"Both with Jose Mourinho, with [Manuel] Pellegrini, with all the coaches they've had.
"If they have done what they have done, winning three Champions Leagues in a row, to take two league titles away from Barcelona when Barcelona in this decade have dominated [LaLiga Santander] like nobody else... I'm so glad that things are going well for them."
Guardiola will come up against Zinedine Zidane in the dugout on August 7 when City host Real Madrid for the second leg of their Champions League last-16 tie, and he only had fond words for the French coach.
"He's good for football, in good times and bad, and I'm glad," Guardiola noted.
"I'm really glad that things are going well for him because people like him are very good for football."