In this corner, we've got Super Mario Bros. 2, a game meant for those who mastered the original SMB, introducing such elements as poison mushrooms, airborne Bloopers, a distinct playstyle for Luigi, a set of challenging bonus levels after completing the main game, and, most importantly of all, cruelty.
In this corner, we've got Super Mario Bros. 2, a decidedly big departure from the genre, system and generation-defining first entry, focused more on tossing your enemies at other enemies than stomping them, as well as a much less linear level design, featuring elements like key-hunts and vertical platforming not found in the original. Still, despite it's disparities with it's predecessor (and the many games that came afterwords), many elements, like Shy Guys, Birdo and playable Peach & Toad would become staples of the franchise.