Gameboy is one of the most successful consoles of all time and it has defeated countless competitors. Virtual Boy just totally flopped. It's easily the worst.
I know a lot of people don't even count the Virtual Boy, because it performed so badly. If you don't want to count it, then Wii U is next.
While it may have the "Boy" moniker, I don't believe that the Virtual Boy is considered a successor to the GameBoy line.