The England winger had a choice of the two clubs after Middlesbrough accepted bids from both teams, and the 25-year-old opted to join high-flying City.
Despite his move not working out at the Etihad Stadium, he still feels he made the right choice at the time.
"I had the choice of going to Sunderland or City, and I probably made the right decision with the medals and the experience I have had," he told reporters. "Looking back, I would probably do it again - I suppose any young lad would in my situation then.
"But it's worked out now that I am here."
Johnson feels his first-team opportunities were restricted at City by boss Roberto Mancini, but admits he enjoyed the success of winning trophies, in particular the Premier League triumph last season.
"You can always look back and think," he said. "It was a slightly disappointing end, but I won the Premier League, FA Cup and the Community Shield and played in the Champions League, so it wasn't all bad.
"But it was a little bit disappointing I didn't play as much as I was capable of. I owed it to myself to go and play football again and enjoy playing."
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