Was there a Game Gear to Master System converter? I remember that a friend could play Mortal Kombat games with one of those on his Master System but I haven't seen one ever since (other than the reverse, Master Gear). Edit: I can't figure out how is this possible since Game Gear has a higher colour pallet.
I thought the Game Gear actually had some features the Master System lacked and that would be why you couldn't play GG games on the Master System. That's what I always remember reading on the subject.
The game gear has a wider array of colours to choose from, 4096 compared to 64 on the sms. But both are limited to only showing 32 of their colours onscreen at a time. The SMS has a higher pixel reslution than the Game gear, 256x192 compared to 160x144 if memory serves me correctly. The Gamegear can also do stereo sound, sms is mono, but I don't think stereo was widely used. Thats all the differences.
Playgeneration is 100 percent correct. SMS games use only one byte for color information, whereas Game Gear games use two bytes. The only GG games that might run on a convertor connected to an SMS are ones that were originally SMS games to begin with (like Sonic or Psychic World.)
The start button on the Game Gear corresponds to the pause button on the SMS. Also, if I'm not mistaken the link hardware on the Game Gear is completely absent from the Master System, not that there were more than three games that used the thing. :/