If it had not been for Giovanni, your adventure in the world of Pokemon might be a bit dull. It is much like that song, "You never know what you got 'till it's gone". When playing Pokemon: Diamond something was incredibly lacking. These goons called "Team Galactic" kept popping up and going on and on about "something-something god Pokemon". Where the heck was Team Rocket? Giovanni, as already discussed as being the leader of this organization, was also in charge of some of the most intriguing plot lines in the original game. We cannot dismiss that he was also the leader of the final Pokemon Gym. What I find somewhat disheartening is how he seems to have left the scenes entirely in the most recent versions of the game. Now the big question is, why is he so important?
Let us set aside the fact that without the particular advances in the storyline in the game, you would not be able to catch the subtle hints of Mewtwo's birth or that he was the original villain of the Pokemon series? He remains that villain to this day even though in the anime and games other groups are introduced, they quickly disappear while Team Rocket remains.
His role in the Pokemon World is very significant. In the Pokemon Adventures Manga it is said that he wrote the only book solely about Ground Pokemon. Since it is his specialty, he is also revered as an expert in that matter. Aside from Team Rocket in the Manga, he also controls much of what goes on the Pokemon World. He has Gym Leaders at his disposal, though, it is unclear if they follow him because of money or for his sheer brilliance. Whatever the case he remains as the Boss (and ex-boss) of Team Rocket, being both his most glorious triumph and his ruin.