While the Gameboy Color was technically superior to the Gameboy the differences between the gameplay is not big enough to warrant calling it the next generation. An example of a next generation Handheld at the time would be the Neo Geo Pocket or The Wonder Swan both released around the same time of the gameboy color and had considerably superior hardware and battery life just as good as the gameboy. If the Gameboy Color was meant to be the next gen predessor to the gameboy Nintendo would have made it much more powerful than it was.
Gameplay, what? What does how the developers made their game have to do with the system? The SYSTEMS determine the generation NOT THAT GAMES. Just because a developer didn't change the gameplay doesn't mean the graphics and how everything ran just don't exist. Pokemon has always been the same gameplay. So are you now going to argue that we never left the GameBoy era?