Why does everybody like Echo the Dolphin when it comes to old Genesis/ Mega Drive games ?

Whenever somebody makes a Mega Drive list, that Dolphin game always scores really high or high up on the list.

It's a game where you play a Dolphin and swim around. What's so amazing about it ?

Yeah I have played it on Sega Mega Drive collection thing, and it was a bore. It was just a Dolphin and ....swimming around.

Am I missing something here ?