Mesut Ozil marked his Arsenal debut by teeing up Oliver Giroud for the opener, before Craig Gardner equalised from the penalty spot for Sunderland.
But Welsh international Ramsey struck a 67th-minute volley before sealing the points for Wenger’s side by finishing off a flowing team move nine minutes later.
"He (Ramsey) is a different player to one year ago in September," Wenger told the media afterwards. "Many people questioned him, so credit to him.
"He works very hard and has improved dramatically. It’s absolutely fantastic what he is doing."
With the score at 2-1, Sunderland’s Jozy Altidore had the ball in the net, but referee Martin Atkinson had already blown for a foul on the USA international outside the area.
And Wenger admitted that his side had received a slice of luck from the official.
"We were a bit lucky at 2-1 maybe, but we found the mental resources to win," he added.
"It could have been a foul for us as well because Altidore took (Bacary) Sagna as well but the referee blew before the goal, I was sure of that because I saw him."
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