What defines something as a Game Boy? Having portability? I suppose we should call Yogurt Smoothie Packs a type of Game Boy!
In all seriousness now, I realize that as Game Boys went on, they began having games only compatible with themselves, while still playing the old games, like GBC could play GBC and GB games. And GBA could play GBA, GBC and GB games. I guess technically, since the DS can play GBA games, it is sort of a Game Boy.