Happy Mario Day! Woohoo! ๐
It's a tie between Super Mario Sunshine and Super Mario Galaxy! I know some people disliked Sunshine having a seaside setting for most of its levels but to me that was just a part of the appeal. The artstyle and fairly difficult gameplay (don't get me started on that pachinko level!) were charming in their own way, and Galaxy's graphics were just amazing. Galaxy's gameplay was unique with the gravity/planetoid mechanic and a part of the story actually made me cry... Mario Odyssey is good but doesn't come anywhere near as close as Sunshine and Galaxy for me. I still replay both games from time to time!
My evil self would've already completed her villain arc in which all of her art would be Pikmin fanart, except it's actually Breaking Bad memes in varying degrees of subtlety.
So I'd become her sidekick and do the same. I regularly pretend to fight myself in the mirror so that I can get really good at fighting with any and all potential clones of myself, so on the off-chance she wants to try and fight me, I have the experience.