What's the diffference in the new Pokemon games?

I was wondering what the differences were with the new pokemon games (Heartgold and Soulsilver) from their old versions from the 1990s. I know some differences, I was just wondering if its worth buying.

I know that you can pick a pokemon to follow you, but my big question is are all the pokemon available in them? Not just the ones from the original, but the most recent. Thanks!!What's the diffference in the new Pokemon games?
It's like the old games with the new regions added in, I think. That plus you get the Tamagotchi type thing with it.What's the diffference in the new Pokemon games?
Its worth buying dude, it has better graphics, good changes, interactive mini games such as Pokethlon.

U can get the pokemons of the 4th generations too. U can catch 410+ pokemons / total 493 pokemons in the game if u have at least one of them.

Ray :)