The 25 year old could have signed for the Black Cats back during the 2010 winter transfer window with then manager Steve Bruce hot on his trail, but opted instead for City.
Johnson said: "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.
"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 admits he will look back on his time at City with mixed feelings, but his spell with the club will also include some big highlights.
He said: "You can always look back and think. 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."