While Jackson also won two championships with the Yankees, he said his years with the A's make up a significant part of his legacy.
"I won three World Series here. I played eight years here, nine when I came back, something like that," he said. "I hit more home runs here than I hit [in New York]. I probably accomplished more here. ... I don't like to compare them, but if I had to say who would it be, I'd probably say the A's."
Jackson was the American League and World Series MVP in 1973, a year in which he tallied 32 home runs and 117 RBIs.
He noted that impeccable chemistry is what set the A's of the early '70s apart.
"We were so good because we played together throughout the Minor Leagues, and everybody knew where the other guy was going to be," he said. "I remember looking to my right and Sal Bando was there, look to my left it was Joe Rudi, and Catfish [Hunter] and Rollie [Fingers] and Campy [Bert Campaneris].
"When you went to war every day, when you went on the field every day, you knew you had a chance to win."
Jackson speculated that those A's could have won even more titles had the team not been broken up after '74.
"I probably think we could have won five or six if we'd have stayed together 10 years," he said. "Of course, what injuries would do -- [but] we didn't have injuries."
Jackson threw out a ceremonial first pitch Saturday night along with Gene Tenace and Fingers, the MVPs of the 1972 and '74 World Series teams, respectively.
Soon enough, Jackson said, the current A's could win a title of their own.
"They'll get a diploma here in a year or two if they stay healthy -- they'll get their doctorate and win a championship," he said. "They've got enough pitching there, and I think their front office knows what to do."
Aaron Leibowitz is an associate reporter for MLB.com.