Why was Mega Man 2 the best-selling Mega Man game for thirty years?
Mega Man 2 sold over 1.51 million copies and held the series sales record for roughly thirty years, until Mega Man 11 passed it. The documented reasons are a chain: the first game flopped just softly enough to leave a door open, a director went over his producer's head, and a small team spent its own unpaid hours fixing everything the public and Capcom's own marketing department had complained about. The game that resulted was not the sequel Capcom planned. It was the sequel its makers insisted on.
THE CHAIN
How an unwanted sequel became the recordStart with permission. The first Mega Man had not been successful enough to justify a sequel, and producer Tokuro Fujiwara opposed one. Director Akira Kitamura appealed to Capcom's vice president and was allowed to proceed on a condition that reads like a punishment: the team would build Mega Man 2 concurrently with their other projects, in their own time. Inafune's memory of those months is the opposite of resentment: twenty hour days, the best time of his years at Capcom, because they were making something they wanted to make, and, in his words, it showed in the game.
Then the fixes. Everything players and marketers had flagged in the first game was answered: the brutal difficulty was softened with support Items and a password system, the Energy Tank let a dying player recover, the boss count rose from six to eight with designs solicited from the fans themselves, 8,370 submissions deep, and content cut from the first game for cartridge space finally shipped. Kitamura's team had three to four months, and spent them on exactly the complaints list.
Then the word of mouth. The first game had been a sleeper hit, building an audience slowly with almost no press; the sequel landed in front of that audience complete. Reviewers ratified it at the time, Mean Machines at 95 percent, EGM's panel unanimous at 8 of 10, and the retrospective canon did the rest: best game in the series in poll after poll, third best NES game ever made in GamesRadar's ranking. Japan's own verdict is printed on the PlayStation reissue's packaging, which calls it, without hedging, the series' masterpiece.