Anakin was destined to fall to the dark side for the Force would only be in balance if the Sith and Jedi are equal. With the Jedi working with the Republic for thousands of generations, the Jedi were too powerful and the light side of the Force was too bright. Anakin then joined Palpatine, destroyed the light, which cast a massive shadow across the galaxy because Palpatine became the emperor.

Luke then helped his father return to the light side of the Force and destroyed the Sith making a great grey area where neither light nor dark dominated. Luke was on the light side, but he was a very dim light compared to the rest of the galaxy.

As for the truth behind what Palpatine tells Anakin about Darth Plagueis and being able to influence midichlorians to stay alive, it may all be true from a different point of view.

It's possible that Darth Plagueis, a powerful Sith lord we're told, would be afraid of losing all that he had. Plagueis may have started to find a way to live forever and used his apprentice, believed to be Palpatine, to reach that goal. Plagueis most likely was getting very powerful when he was able to help others stay alive. Palpatine learned it all and saw his master as a threat to him, so Palpatine killed his master.

Palpatine may have worked on the techniques himself but wasn't as good at it as Plagueis. After all, Palpatine planned to destroy the Jedi and take over the galaxy which took quite some time to achieve. After the Empire had come to power, Palpatine probably spent more of his time working on living forever for he was now the top being in the galaxy and didn't want to lose all that.

In seducing Anakin, Palpatine knew that it was possible to help others stay alive, but wasn't a master of it. Then again, if Anakin was destined to join the dark side to bring balance, maybe Plagueis was destined to discover a hint of being able to stay alive and he was destined to pass the knowledge on to Palpatine. This would let Palpatine be able to seduce Anakin with some truth behind what he said.

This is what I get from Revenge of the Sith, both the book and movie, as well as from watching all six movies. I may be right on some parts, or I may be so wrong that I'll laugh at all this later.