A brilliant copy of an alright game.
This effort is remarkable. From the number of characters selectable to the presentation, to the graphics, to the remarkably 'accurate' controls.
However, I can't bring myself to play more than one act. I just can't help feeling that there's little point spending time playing this when there are better, official, versions of the game.
I personally feel the series went a bit downhill after #2 and it was always about the feeling of speed over interesting design - something which is far more of a novelty and which your version doesn't recreate quite as well as it might.
There are a few missing frames of animation, resulting in some unsightly occurences when slowing down at an angle.
Being killed during the 'bounce back' as we lose our rings seems unfair - far more bastardly than the original and needlessly so.
But it seems churlish to chide you for not having a perfect clone.
I just wish that you could match your obvious determination and programming skill with some more imagination and top level design.