MM7, Rockman & Forte, MM8, MM9 and MM10. Game Time is used here, since the games are spread out over 3 different systems (at least).
40 robot masters rules:Timing starts on "Game start" in Mega Man 7 and ends on last hit on last robot master in Mega Man 10. A robot master is a boss whose power you get after you defeat them. After you have defeated all robot masters in one game (and collected their chips in MM9), switch to the next one right away.