Although I never owned it, this is technically the first game I ever played. Good start.
On a recent replay I realised how great it actually is. It's short and sweet but just open enough in design and with just enough secrets to keep me coming back to levels. More than anything though this game is incredibly weird and wonderful. There are whole videos out there describing the ludicrously dynamic sound design.
We'll probably never get another Wario platformer since they only make the minigame collection thing now. A damn shame...