Having moved to Old Trafford for a fee of around £26.3 million, Mkhitaryan made 63 appearances in 18 months for Red Devils, scoring 13 goals.
The Armenia international was not always an automatic starter under Jose Mourinho, however, and spent two long periods out of the team under the former Chelsea boss.
He eventually left United in January as part of the swap deal that saw Alexis Sanchez move from the Emirates Stadium in the other direction, and laid on three goals in his first start for the Gunners against Everton.
"I think I left an impression in Manchester, although I had difficulties," he told SFR Sport. "We won three titles in a year and a half — not every club does that.
"We won the Europa League, and I scored a goal in the final. If people say that I did not have enough success it is their opinion but I believe that I had a lot of success at the club."
Mkhitaryan's relationship with Mourinho came under plenty of scrutiny during his time with the 20-time English champions.
And though he retains the belief that Mourinho never had any personal issue with him, Mkhitaryan thinks new manager Arsene Wenger's more understanding nature should help him thrive in north London.
"Mourinho required a lot from his players, he was very hard," he said.
"Arsene Wenger is more friendly, he understands and can think about players' situations. He is calmer — that's the difference.
"Wenger's philosophy in three words? Play football, win the match and enjoy.
Asked whether he felt Mourinho had confidence in him at United, he added: "Yes, of course."
Mkhitaryan is set for his first taste of a North London Derby on Saturday as Arsenal travel to Wembley Stadium to take on Tottenham.