Pity we never got the arcade System 18 ver. of Shadow Dancer at home.
Indeed. It would have been cool to have a two-pack that contained the original arcade Shinobi and the arcade Shadow Dancer for the Genesis, or to be arcade-perfect, the Saturn.
The Master System version of Shadow Dancer is actually quite faithful to the arcade version. Unfortunately it omits some of the stages, probably in order to squeeze it into a two mega cartridge. But the sprites and backgrounds seem to be adapted directly from the coin-op.