Super excited for this, personally. Crystal was so revolutionary in the progression of Pokemon games. The key aspect being the first game to allow you to choose between a male and female characters, another is being the first to animate its sprites going into battle. It will be an incredible act of nostalgia for a good handful of members on this board, and for people across the world. My wife in particular, her first game was Pokemon Crystal. I know lots of people who got into Pokemon with Crystal (likely because of the male/female option) and then Ruby and Sapphire. This game, I believe, was monumental in the growth of Pokemon's popularity.

I do want to say, though.. As far as main series games, Crystal is actually the only game solely for that console. Gold and Silver are actually still playable on the original Gameboy console. Alternatively The original RBGY games were playable on the GBC, and you got color in those games, even though they were made for the original Gameboy. Pokemon Yellow, specifically, because it was more 'Full Color' than the other three. After that, I believe Pokemon Puzzle Challenge is the only other game solely for the GBC console (I don't count the TCG sequel because it was only released in Japan and incredibly under the radar. :P).