The first Mega Man sold modestly; Capcom let the team build a sequel almost on the side. Mega Man 2 (1988/89) is the one that turned a cult game into an institution.

The loop is pure design candy: pick any of the eight Robot Masters in any order, beat one, and the weapon you earn shreds another — a rock-paper-scissors puzzle wrapped around razor-sharp platforming. Metal Blade is still arguably the best weapon in the series.

And the music. The Dr. Wily stage 1 theme is one of the most beloved pieces of chiptune ever written. Hard, fair, and endlessly replayable — this is the NES action game I come back to most.