If you're talking about Battletoads, then I've no idea what the megadrive one was like, but the Megadrive version of Micro machines was excellent.
It's pretty much identical but I'd put the Amiga one above it for sound, and the megadrive one above the amiga one for loading times.
Micro Machines 2 (in it's various forms) on the other hand was AWESOME on the megadrive. The addition of the cartridge being a "J-Cart" made it sooo much better. (J-Cart meaning that the cartridge had two joystick ports on it so the game was 4 player without the need to buy a multitap!)
It was actually 8-player but that involved sharing pads, ugh!