The former City winger has FA Cup and Premier League title winners' medals from his time at the club, but thinks that winning a trophy with Sunderland would surpass those efforts.
"Winning the cup final with Sunderland would match anything I achieved at Man City," Johnson told The Telegraph.
"City are going to win a lot of things. It was great to be part of the first team that won the FA Cup there for 40 years, but if you win a cup here, you'll go down in history.
"It would complete the hat-trick of domestic competitions for me as well, which would be nice.
"We have come so far as a team, we were so low a few months ago, so to get to a final and have a chance of winning the club's first trophy since 1973 is incredible."
Johnson looks back on his time at City fondly but admits that a victory over his previous employers would be extra special.
He added: "It's ironic the cup final is against City, I don't think there is a team I'd rather face.
"Everywhere you go at Sunderland there are reminders of the 1973 FA Cup final team. There are pictures up at the training ground and this club has a proud history.
"We want to write our own chapter. We want to have our picture up on the walls in colour alongside the black-and-white ones."