What is the hardest Mario game

Well it depends, if you just play for fun, it's probably RPG's series (Super Mario RPG: Legend of the Seven Stars, Paper Mario, Paper Mario: The Thousand-Year Door, Super Paper Mario, Mario & Luigi: Superstar Saga, Mario & Luigi: Partners In Time, and Mario & Luigi RPG 3). If you don't like RPG series, and you like simple 2D games, then you should definetly Play SMB: The Lost Levels, or Super Mario Bros.2 (Hardest Games). If you 6 years old or smaller and you have no clue how to type, Mario Teaches Typing, and Mario Teaches Typing 2 will not be the hardest, but It will take a lot of time to finish it! If you like to complete 100% of game, then play Super Mario 64 DS, Yoshi's Island DS, Super Mario Sunshine, Super Mario Galaxy, and New Super Mario Bros. Original Mario Bro. is pretty hard, too. Donkey Kong and Donkey Kong Jr. are hard but they are too short. Mario Party series are hard, too. Ok, so you get the point, you just have to play couple of games and you decide, because everyone plays different. But I can tell you the Hardest Boss of all time. It is Optional Boss from Super Mario RPG: Legend of the Seven Stars! But the best (doesn't have to be hard) Ten Mario Games Are: 1. Mario Kart Wii and DS (almost same) 2. Super Mario Advance 4: Super Mario Bros. 3 (better than original) 3. New Super Mario Bros. 4. Brain Age 2-Virus Buster (updated version of original dr. mario) 5. Super Mario Bros. 6. Yoshi's Island DS 7. Mario Party 8 and DS 8. Mario & Sonic At the Olympic Games (DS) (Wii version sucks) 9. Mario & Luigi: Partners In Time 10. Super Mario All Stars & Super Mario World (2 in one)