A Gameboy Color? Seriously?
I remember the best game ever for the Gameboy Color being Pokemon, wasting countless hours of my life.
There was also Yugioh Dark Duel Stories which I enjoyed (but the rules don't follow that of the actual Yugioh rules)
The Legend of Zelda: Oracle of Seasons has to be one of my all time favourites.
Robopon; Metal Walker (I think that's what it was called); and Lufia were also great.
There is no Knowledge that is not Power