I think even after all these years I still have to give it to Mario 3 - such imaginative colorful environments, perfect controls, appealing gameplay, difficulty that's mostly just challenging enough to be exciting but not anxiety-inducing or unfair. Just about every aspect of the game is perfect.
Though Zelda BotW is a close contender for 2nd - such a rich, dynamic game that looks gorgeous and play fantastically. In-depth but not overwhelmingly complex. A sort of callback to the open-world sensibilites of NES Zelda while still being very flashy and modern.
Smash Bros. Melee and Mario World are also close runners-up

"We hold these truths to be self-evident - all men and women created by the, go-you know.. you know the thing!" - Joe Biden








