CastleMania Games is now selling the open source Master System to game Gear cartridge adapter, that was first announced in July of last year. This allows you to play original Sega Master System cartridges on your Game Gear. You can also play SMS roms on a GG via an Everdrive, however this is specifically for people who want to use original cartridges:
Purchase MS2GG: http://bit.ly/ms2ggadapter
Everdrive GG: http://bit.ly/everdrivegg
I remember playing SMS games on my Game Gear when I was a kid and thought it was the coolest thing in the world! While yes, the qualityon the original screen was pretty terrible, there was something magical about playing a console cartridge on a handheld! I’m not sure if this would be the best way to experience SMS games, but there’s a few scenarios where I bet it would be a lot of fun!
As a note, you’ll need to keep realistic expectations on how this will look, as you’re essentially squishing the SMS’ 256×192 resolution into the Game Gear’s 160×144. I’ll have a video showing details on this soon, but if you’ve installed a modern LCD screen you’ll have a better experience: