Sure, in his younger days before Revenge of the Sith he was good but the the first thing he did when turning to the dark side was to kill a bunch of Jedi kids. Who knows what other evil things he did in the time it took Luke and Leia to grow up but we know he was instrumental when the planet Alderaan was destroyed. Then he killed Obi Wan. After that, he tried to turn his own son to the dark (evil) side. The only good thing he did after turning to the dark side was to kill the dark lord but that was only because he was killing Luke.
Vader did bad things but I don't think he was anything like the Satan-like figure in the movie or Satan himself. Vader still had good. And he had a strong inner conflict in the last movie, "Return of the Jedi," with his good side prevailing as a result of killing the emperor. I think Vader had good in him. The time for redemption had to come.
All of them were good, but Obi-Wan Kanobi comes into question, especially in the prequels. Some people say he was extremely deceitful, yet the sequels portray him as good.
But between Luke and his father, there was no difference. Luke had strength to remain good, that's the difference. Anakin was easily influenced because of the loss of his mother...
He just wanted to save Padme. It was all Palpatines fault. He had good intentions and was ultimately good in the end, saving his son Luke. Look, he had a hard life and went through tough situations. Im not surprised he turned out how he did, joining the dark side.