You made my original point exactly. The Master System games were ported perfectly on the Game Gear not because the Game Gear was amazing technology, but because the Master System wasn't as good as the Genesis. The Genesis was the TRUE competitor to the NES while the Master System was more like a giant home system that played portable quality games. The GameBoy didn't play ports of Mario or anything. It got its own games because it was way less powerful. So my point was if NES games can be on the eshop, why can't Genesis games. Game Gear games being on there is just like having Game Boy games on there. Yea they're great, but if NES games can be on there, Genesis games would be the equivalent, not Master System/Game Gear.
Actually, the Game Gear played Master System ports, not what you said. The reason we didn't get SMB3 on the Game Boy but the Master System and Game Gear share a library is that the Game Gear is the Master System's equal. The Game Boy wasn't as powerful as the NES. God forbid Sega do something better than Nintendo though, right?