Porting a game from Sega is really another story than from the Atari ST, for sure.
The megadrive has some strange video chip, which we probably can't emulate in real time (unlike converting the ST screen).
There also is some kind of FM synth chip coming in the way.
In comparison, the embedded z80 is little problem ; its code can be disassembled and converted. But nevertheless.
So "porting" a game is probably more a matter of 100% rewriting the code and pre-converting the graphics.
Of course if someone has a good screen conversion routine and is able to emulate that FM chip, i would port Sonic, lol
