Amy is not a forgotten character in anyway. Even if she isn't on par in Popularity with the others. She still manages to have some type of role in every Sonic game to please most of the Female Sonic fans. She even got a role as playable in Mario & Sonic. When she is considered the Peach of the Sonic team. So Amy should not even be mentioned in "Forgotten characters". (As for Fleetway Amy, that only happened because in the U.K. a Female Indivulization group was around. If they were not there, Amy whould still be the same "annoying whiny girl" that she is IYO as the games. The fleetway comic is weird anyway IMO)
As for Sally, she is not a forgotten character UNOFFICIALLY. Since she still has a prominent role in the Comics, as for games. She has only appeared in cameos such as in Sonic Spinball and if you can count all the comic scans in Sonic Mega Collection. Amy was orginally going to be Sally in what perhaps was a prototype of the Manual of Sonic CD. But a New character was made instead. So technially Sally is in fact a forgotten character in the games, but is not forgotten in the area she 1st appeared in: The Comics. And thus, 1st appearing in Comics breaks the 1st rule of Sakauri's character role. Sally won't even get a mention in Brawl