Pokemon Gold is the Pokemon series at it's best.
I may be over exaggerating the quality of this game, but I'm not trying to. Pokemon was something that was so expansive before the Gold and Silver games, it was hard to fathom how much you could do in the Pokemon games (especially for the young ones). They were truly the games that kept on giving.
Anyway let's get on to the plot of Pokemon Gold Version.
Pokemon Gold takes place three years after the Red and Blue Versions. You play as a kid whose dream isn't necessarily to become a Pokemon whiz at first. All he was asked to do was to deliver a package for his good friend Professor Elm (who lets him borrow a Pokemon for his travels through the dangerous wilderness) when he winds up meeting Professor Oak (from Pokemon Red and Blue) who scrambles everything up for him after he gives the poor kid a Pokedex. After he gets the Pokedex, he returns to his home town (after he gets an urgent call from Elm because there was a robbery at the lab OMG!) and after running into an emo kid on his way, returns to the lab and he is forced by professor Elm to embark on a quest to become a Pokemon champion because Professor Elm assumes that since Professor Oak gave him a Pokedex and he got back in once piece, he could make it to the top... alright. So, Elm gives the kid the Pokemon he was borrowing and the adventure begins! Like the first games, the main goal is to acquire Eight badges from Gym leaders. After you get all of the badges, you are able to challenge the greatest Pokemon trainers in the region (the Elite Four) and after making your way through them you challenge the Pokemon Champion. Then if you can beat him you become the new Pokemon Champion and all of a sudden, everyone loves you!
Now in the first Pokemon games, that's where the story ends, but Gold and Silver went beyond the main goal that the series first established (and still uses in the new games).
After becoming the Champion, you get the chance to tour the Kanto Region. What's the Kanto region you ask? Well, it's the place that you play in Pokemon Red and Blue versions. Since it's been three whole years, things have changed, which is what makes this part of the game one of my favorite moments in gaming. I won't spoil anything that goes on in that part, but let's just say that a lot of fan service happens.
May I also add that Pokemon Gold and Silver added a whole lotta new Pokemon to the roster, which makes collecting them all even more satisfying than in the previous games.
Pokemon Gold didn't just rehash the series formula before, but it improved on it with flying colors. One of the most noticable enhancements is the fact that Pokemon now have genders. So what does that mean? It means that Pokemon can make offspring with each other.
After Pokemon Gold and Silver versions, Ditto got VERY useful.
Another very nifty new feature is a visible exp. bar. Gone are the days of either guessing when your Pokemon are going to evolve or constantly checking how many points are left by going into the Pokemon's info page. This is very helpful believe it or not.
What else? Oh yeah, the whole game was in color and the graphics put the original's to shame. Gold's graphics looked very good for the Gameboy Color, some of the best on the system.
Then there are all of the little bonus features added into Gold. Like the fact that you can print out pictures of Pokemon you've caught with your Gameboy Printer and you can even play Gold on the Nintendo 64 with the good old Transfer Pak which also allows you to use your team on the big screen in Pokemon Stadium 2.
All in all, Pokemon Gold (and Silver) are probably the most important games in the series. They brought so many things into Pokemon that are still used today, and had enough content to satisfy a gamer for months. Excellent game, can't really go wrong with it... unless Pokemon isn't your thing.