Super Mario 64 - Bowser
Each encounter with Bowser in Super Mario 64 is basically an iteration on the previous fight with him. The difference is the level of challenge and, because you don’t fight him all that often, that challenge outweighs the familiarity.
In Super Mario 64, the player controls Mario atop a large platform while Bowser tries to annihilate you with his flame breath. The primary goal is to get around to the back of him so that you can grab his tail. You twirl him and toss him at one of the bombs around the perimeter, which both feels and looks satisfying.
There’s a tendency for Bowser fights to be entertaining in Mario games and I could have listed several examples. Luigi’s Mansion has a solid fight, and chasing Bowser down in his monster truck tractor thing in Super Mario 3D land is fun for one to four players. Rarely does Nintendo get these fights wrong.