My list as I see it- Super Mario Bros Super Mario Bros The Lost Levels Super Mario Bros 2 Super Mario Bros 3 Super Mario Land 1 Super Mario Land 2 Super Mario World Super Mario 64 Super Mario Sunshine Super Mario Galaxy Super Mario Galaxy 2 Super Mario 3D World Super Mario Odyssey Super Mario 3D Land New Super Mario Bros New Super Mario Bros 2 New Super Mario Bros Wii New Super Mario Bros U
Now this is where it gets tricky Are Mario Maker 1 and 2 count too? What about Super Mario Run? it IS a Platformer where you play as Mario Also, Yoshi's Island is callled Super Mario World 2 - Does it count? (I think there was a poll about this a few years ago in this board..I don't remember the results)
The 18 is the list I most frequently see (no Maker/Maker 2/Run/World 2)