I did a little googling after the comment responses to the question and found some pages that help to answer this question.
At first glance, it seems pretty straightforward that the Super Mario Brothers games are a fantasy series. They take place in a fantastic world with dragons, princesses, and magic mushrooms. The RPGs in the series have all the typical role-playing elements of a fantasy game. But when you look at the entire franchise, particularly the Super Mario Galaxy games, it seems almost certain that the game is science fiction, or at the least, science fantasy.
Either way this article says that Super Mario is on topic here.
This forum seems to come to a consensus that it is Fantasy:
Fantasy/action. The princesses and turtle people root it in the fantasy topic, whilst action is a broad enough genre to easily envelop most platformers.
IMDB classifies the movie as a Fantasy or Sci Fi movie:
Adventure | Comedy | Family | Fantasy | Sci-Fi
Yes, Super Mario Bros is on topic.