To start things off, check out this action figure that never got made. This is a prototype of Toy Island's SA1 line in a prototype package, even. This one appears to be blistered onto the card, where the final had a plastic box construct on the card. The other differences you can notice are:
Board has color on the top, the rings are much larger than normal, there is only 1 emerald enclosed, and the sculpt for Sonic's head is very different. This one has a more slanted eye style, giving the figure a more aggressive look. The figure is also shiny, whereas the final had a more rubberized head material.
The card remains essentially the same as the first release.