Why did Darth Vader continue to serve the Emperor even after he knew that he was tricked?

I think one of the main character traits of Anakin is that he was really susceptible to being "on the dark side". Even after he knew about all the facts, he was so taken over by the dark side of the force at that point that he didn't go back. In addition, the emperor is the one that helped him to survive after his fight with Obi-Wan, and created Darth Vader. Anakin was just a bad guy, fated to rule the dark side of the force.