Several examples are really bad. Deadpool, Elongated Man, and Punisher were clearly meant to be disposed or forgotten, but the fans elevated them. Nightwing or Miles Morales have not gone beyond their role.
Nightwing did graduate as a character, but his role isn't proportionally bigger. Initially, he was created to appear in all or most of Batman's montly stories. Batman has several titles now, that's an increase, but Nightwing doesn't appear in most of them. Both characters grew in popularity, but Batman a lot more. That's not a breakout for Dick Grayson, who now has to share spotlight with a zillion Robins.
Several examples are really bad. Deadpool, Elongated Man, and Punisher were clearly meant to be disposed or forgotten, but the fans elevated them. Nightwing or Miles Morales have not gone beyond their role.
Nightwing did graduate as a character, but his role isn't proportionally bigger. Initially, he was created to appear in all or most of Batman's montly stories. Batman has several titles now, that's an increase, but Nightwing doesn't appear in most of them. Both characters grew in popularity, but Batman a lot more. That's not a breakout for Dick Grayson, who now has to share spotlight with a zillion Robins.