Anakin's rise to the Dark Side wasn't just because of his angst with his love issues alone thought that was the primary factor that instigating him becoming the Sith Lord. It was because of a number of things happening to the Jedi Order and the Council specifically, who showed themselves to be a bunch of hypocrites. Having already flirted with the Dark Side of the Force, he was more prone to turning to the other side.
You have a young man who's been away from all that he knew for years. He's been far away from his mother ever since he was taken at the age of eight. He comes back, on his own free will I must add due to a vision of her dying, to see her. He only finds her broken body and her in her last moments. She was a slave her entire life before she was freed, and now she's dead. At least she saw Anakin. But how did that make him feel? Well, he butchered a bunch of men, women and children responsible for it. Still . . . his dream was to see his mother freed, and that was taken away from him. Being fatherless, his mother was the best thing that happened to him and now she's gone.
Padme comes along, and Anakin falls in love. When visions of her dying begin to surface, he does what needs to be done. He wants nothing more than to save her. Mind you during before that he's already planning on leaving the Jedi Order as a result of his secret marriage that we all know was forbidden. But when he gets the visions, he wants to fix it. He wants to turn things around and not allow his nightmares to come to pass like it did with his mother, because all that he has now in his life is Padme. So after all he's done with for Jedi and all he's done for the Republic, he expects to be granted mastery, as it would give him access to the holocrons that only a Jedi Master has access to.
We know he's not given the rank of master, and that is what drives him into the path of anger. He already dislikes Mace Windu due to his coldness and attitude towards him. He doesn't like Yoda because Yoda wasn't always in favor of his training. The entire Jedi Council was against it. And that denial of mastery was plainly like a slap in the face. So the only person helping Anakin up onto this point was Palpatine and Obi-Wan.
Palpatine tells the story of Darth Plagueis, the Sith Lord who could cheat death. Palpatine temps Anakin, and Anakin becomes Darth Vader after Mace Windu tried to assassinate Palpatine for being a Sith Lord. He goes on a killing spree after he became a full-fledged Sith. He serves his new master by killing the new enemies of the Republic, which are the Jedi. Both men, women and even the children(who could grow to become a threat for the newborn Empire) were executed. Darth Vader then goes and slaughters the Seperatists leaders to mark an end to the war. He believes he's a Hero. And he is, to the side of the Sith.
"From my point of view, the Jedi are evil."
"There are heroes on both sides."- Episode III opening crawl.
Basically, Darth Vader lost faith in the people he served. And when transforming into a Sith, an individual consumed by the Dark Side that accepts no mercy, shows no pity and has a no-nonsense attitude to peace, he goes onto believing what he is doing is right . . . to save the woman he love. But in the end, because of that rage and anger, he killed her. Its ironic. Just like the story of Darth Plagueis. He could save others from death but not himself. Anakin feared his wife's death so much that he did everything in his power to try and prevent that vision from coming to pass, when in fact it was because of his efforts and his turn to the Dark Side that she died. Its a great story, and an epic tragic tale. The reason the movie wasn't good because it didn't capture the entire feel of it. Thankfully the EU did.
Speaking of Clone Wars,
this is the best thing that's happened to that cartoon. Hands down. Always was a fan of Darth Maul. I squealed like a fanboy.