The duration of the story mode in Super Mario Maker 2 isn't fixed. It could be anywhere from 5 to 10 hours or more, depending on how quickly you progress and how much you enjoy taking your time to discover all the features and levels.
The length of the story mode in Super Smash Bros Ultimate is quite subjective. If you're a skilled player and move through the levels efficiently, it might take you around 10-15 hours. But if you take your time to explore and enjoy all the content, it could be much longer.