Antoine Semenyo was the standout performer in Seoul, capping a superb display by setting up both of Omar Marmoush's second-half goals as City overturned a first-half deficit.
His replacement, Rayan Ait-Nouri, added late gloss to the scoreline, while Savinho also posed a threat down the opposite flank. The influence of City's wide players has been notable throughout the tour, with Semenyo contributing four assists across the three games in Hong Kong and South Korea.
"Overall, today was a very good test against one of the best teams in Europe," Maresca said. "Credit to the players for the effort they have done. From tomorrow pre-season is finished and the real business starts.
"I think wingers can play well, but the end product is the most important thing. I think the first half was a bit unfair - we created four, five chances. But the difference was inside the box. We didn't score. The big difference was there.
"But for sure you need a player out wide who can create unbalance, especially when they go one v one."
Manchester City created several openings in the first half without converting them, falling behind before fighting back after the interval. Maresca said the message at half-time had been clear: those chances needed to be taken.
"We could not create the amount of situations we did and not finish the action," he said. "There we need to be clinical - it's something we need to improve. Slowly we are getting there and with Erling [Haaland] we can be even more dangerous.
"Today Omar scored twice - this is a boost - and yes I am happy with that."
The Italian, who succeeded Pep Guardiola at the Etihad Stadium this summer, said he was encouraged by his first three games in charge, with the squad already showing signs of adapting to his ideas.
"I'm very happy. Especially because the players since we started have been open-minded," Maresca said. "They want to understand and want to learn why we do things.
"I know that when you join a new club you try to install new patterns or different ideas, the most important thing is we are getting better.
"But the path is a huge path to improve things. But I can see we are trying what we do in training, and we are getting better at that."
City's tour also included a draw with Inter Milan and victory over the K-League All-Stars, and Maresca's side will now return to Manchester to prepare for the Community Shield against Arsenal, before their Premier League campaign begins the following weekend.