Clashing Sabers posted a pretty good piece about Anakin and Darth Vader. This centers on the idea Vader is essentially stuck in his own trap:
When we meet a young Anakin Skywalker in Episode I, he is desperately trying to be seen not as a slave but as a person. Ironically, and sadly, the same can be said for Darth Vader. He knows that the Emperor sees him as a tool, and he hates himself for it. He wants to be known for who he really is, but the Emperor has just placed him off to the side until he is of use. Again, he has become a slave.