In the 3rd episode of the series ("The Revenge of the Sith"), in the ending we see that Anakin kills Padme. Then he fights Obi Wan, loses and the Emperor saves him. When Vader asks if Padme's alright, Palpatine explains that he "killed her in his anger".
In this moment for Anakin should be clear that Dark Side was wrong way to follow, that Sith way of living (in short: emotions) did not provide anything good and Jedi way (in short: reason) was better.
However, in one of the last scenes we see both of them watching construction of the Death Star and of course we know that Palpatine was Vader's master ("The New Hope" and so on) for next 20 years.
I can't realize that for 20 years Vader could not realize that following the Dark Side made him kill Padme and he was somewhat betrayed by Palpatine. Is there any explanation for this?
(I saw only six Star Wars movies, no books etc., nor I have not watched "Clone Wars")