SMW YEAH!! is one of the more commonly recognized Japanese hacks, known for combining exciting custom sprites with level design more closely reminiscent of the vanilla Super Mario World. It features 51 Exits over five worlds, a secret reward for collecting all Dragon Coins and a sort of mini-puzzle spread over multiple levels, which you need to solve in order to gain access to the hidden special world.

The game is an interesting piece of SMW hacking history, as it was highly influential when it was released and is still considered to be one of the best hacks to come out of that time period.
Ultimately, it's one of those seemingly rare hacks that feature both an accessible difficulty curve throughout the entire game and engaging gameplay at the same time. This makes it a worthwhile hack to try out, especially for people new to playing SMW hacks.

This version of the game is an English translation that includes various quality-of-life improvements.

51 Exits