I will agree with Chimp, it was named a classic because of the originality. Other than that, I loved it, I still play it from time to time. The full range of motion was amazing, made some levels seem endless (when I first started playing it.). What really impressed me was flight using the Wing Cap. It added so much more fun, being able to scope the level out from the skies. And when that got boring, there was always Shell Shredding, which was fun for jumping pits and squashing enemies.
In retrospect, it was an amazing game!
Cheers,
Maj