New Super Mario Bros. Wii, mostly because there is a Wii and a Super Mario-loving kid at my mum's house, so there's no real reason to not have played it. Although I suppose I could always try to find it cheap somewhere and leave it at their house. My heart is aching to play Odyssey but I don't own a tv, so I hope that my mum's husband is gonna buy Switch so I can play when I visit. I would love to get to play Yoshi's Island, Super Mario Land 2 and Super Mario 3D World as well. Some day.
Every GBA and DS Mario game, especially Yoshi's Island GBA, Yoshi's Island DS, Partners in Time, Bowser's Inside Story, Super Mario 64 DS, and Super Princess Peach.