When THAT game was being made, the developers took the successful formula of Donkey Kong Country and actually took the time to develop completely different levels for the Game Boy incarnation, so the whole game felt like you were playing a bunch of additional levels that could have very well fit into the first Donkey Kong Country game.

However, I guess I can't criticize the game too much as I can think of a small handful of great trilogies that were somewhat tainted by an under-performing game