Contains light spoilers and obviously this is just for fun.
Does this make any sense, or is it the ramblings of a crazy person?
First the Chararacters: Mario is Joel, Peach is Ellie, Sarah is Pauline, Bowser is David, Luigi is Tommy, Goombas are cordyceps, Koopas are hunters, Tess is a toad, Marlene would be Donkey Kong (the original), and Bill would be Wario.
Gameplay: The combat focuses mostly on melee with the addition of firepower every now and then and literal fire being your best friend when it comes to wiping out enemies. Also the world you exist in is very inhospitable despite normally looking very calm on the surface, and pretty much everything that moves will try to kill you. Both also feature non-regenerating health and you can only heal through the use of health found in boxes in the environment. When you find excess health you can store it for later (the savable power up in mario games). Later on there is gameplay with up to 4 characters, but it's the most tense when it's you all alone.
Story: The fireflies being at another place each time is like the princess is in another castle. It keeps getting your hopes up just to say nope, try again next time. There's also a theme of kidnapping. Bowser putting peach in a cage, David putting Ellie in a cage. There's also mutliple rescues. Last but not least, both main characters have awesome facial hair.
Peach isnt a kid, and i think mario loves Peach so uhhh no just no
She isn't a kid, but their relationship is pretty plutonic. You might assume that they are closer but they've never been shown to have had any kind of relationship.
Mario 2 (what 3D world is semi inspired by) has 4 different characters.
Wario is not Mario, he's like Mario but crazier. Bill is like Joel but crazier. Bill only helped Joel out of fulfilling a debt and slightly caring about him, but really they just don't get along.