Nice work!
I jumped near a tunnel, went through a wall, and got stuck with a ramp to the ceiling on the left and a loop I could not enter on the right. Also, I recommend making some kind of indicator for the currently selected character on the character selection screen to let players know which character is currently selected. A background bar, an outline, an arrow, or a color change perhaps?
Aside from that, you have done some very nice work. You should polish it up a little bit then submit it to Sega; maybe you can get a job doing Web stuff for them.