Another thing the Megadrive had as a slight advantage was the cartridge, these could add custom processors or boost the memory of the Megadrive itself which the coders could use for their title.
Most of the Megadrive (and SNES) games were developed by the original developers (Capcom, Sega, Konami, etc.). In most cases the Home Micro users had to put up with the likes of US Gold handling conversions. In many cases the games were not optimised to run on the Amiga so features were cut out as companies like US Gold were just interested in getting titles on all the possible formats they could.
Coders such as the ones from Team 17 and Bitmap Brothers showed how games could be when designed from the ground up for the format.