The original Pokemon Gold and Silver are considered by fans to be some of the best Pokemon games ever created. They introduced an innovative "time of day" system, where the environment changed alongside time in the real world. In particular, the types of Pokemon players could catch in certain areas and certain events would only happen at specific times of day. It gave the a games a more realistic flavor and an extra dimension — an extra challenge --players had to understand in order to "catch 'em all."
But sadly, there was an unexpected consequence of the "time of day" system. In order to keep the time, there was a small internal battery that ran constantly --even when the game was off. Unfortunately, as time went on the internal battery drained away, making it impossible to save your game. Some of the more tech-savvy players were able to open up the cartridges and replace the battery, but most players could not, leaving many older versions of Gold and Silver virtually unplayable. Happily this problem is corrected in Nintendo's update to both games, HeartGold and SoulSilver.
In HeartGold, just like in other Pokemon games, you start the game as a new trainer who is trying to capture all the Pokemon out there. You train your Pokemon; beat other trainers; gain experience; win gym badges; battle your friends; be the best; and, most importantly, catch 'em all. Best of all, after finishing the game, you unlock the ability play through the areas from the original Pokemon Red and Blue games.
The original Pokemon Gold has been given a massive face-lift to look like a modern DS game and the creators have packed the game with plenty of nifty little extras. Probably my favorite was the addition of the Safari Zone, which had to be cut from the original game due to space limitations on the old GBA cartridges. This version is also equipped with the WiFi abilities of other Pokemon DS games, and is fully compatible with them, so friends can challenge one another to head-on Pokemon battles or minigames. Perhaps the best thing this game brings to the table is the fact that the original 150 Pokemon are now available on the DS, meaning that every Pokemon in existence is now part of the DS universe. HeartGold even utilizes the touch screen completely, maybe even a little more than the other Pokemon DS games.