Best pokemon game by far, it's only peer is silver version!
As far as graphics and eye-candy goes, this is a much bigger step above Red/Yellow/Blue. Smoother animations and much clearer visuals. Not to mention that its VERY colorful and completely takes advantage of all the colors the GBC can use! Also, in battle looks a lot better than in the previous versions. Animations look better and battles progress a whole lot faster!
As far as gameplay is concerned, its hard to put Pokemon Gold/Silver down. There is a new feature introduced in this game that once again shows that the GBC is more than we think it is. The internal clock has made the gameplay so much more interesting. The game actually changes between day and night and it changes based on how YOU set it up! Not only that but pokemon only come out at a certain time of the day. Some come out in the early morning and others come out at night!
Catching Pokemon hasn't changed much from Red/Yellow/Blue. The difference is that you now have several different kinds of pokeballs. You've got Heavy Balls to capture Heavy Pokemon, Level Balls that catch pokemon at rather low levels, Marine Balls for catching water pokemon and the list goes on.
The other interesting tidbit is perhaps the Pokegear that is introduced and the Cell Phone feature. The Pokegear makes it so you can carry more than just 20 items like before. You've got a seperate pouch for Balls, Key Items, TMs and HMs and just your normal healing items and such. The Cell Phone feature is nice and probably one of the best additions to the game! After you challenge some trainers you can ask them for their number. When you have their number they'll call you and do a few things. Some wlll ask for a rematch, some will tell you of Pokemon Swarms, some will give you an items. Most of the time, however, trainers will call to tell you stupid things, such as the status of their pokemon or how they beat other trainers.
Of course the whole story is to become a Pokemon Master. You get to explore a new world of Johto but in the end you'll end up having a nostalgic time in Kanto (the setting of Red/Yellow/Blue games) but in a different sense that once you defeat the elite four, you'll have to start a new journey and ultimately you'll end up fighting the toughest trainer in the game (the hero from the Red/Yellow/Blue Games).
The small gripes with the game. Well, for starters the Random Encounter rate is high at times which is rather annoying. Second, some trainers are just imopossible to dodge. In fact on most routes you'll have to fight all the trainers and it isn't by choice. You fight them because you HAVE to.
The music is great! In Johto at least. In Kanto the remix music of the Red/Yellow/Blue versions is terrible. Not to mention that when you get to Kanto, all the Pokemon are of low levels and are actually the exact same level they are in Red/Yellow/Blue.
The game is worth the buy though. This is one of thsoe addicting games that you'll find yourself coming back to over and over again and the best Pokemon game of them all! If you like Pokemon get Gold or Silver.