While thinking of Star Wars as a tragedy may not make sense at first, if you go through the list of characteristics which make a tragedy almost every single one applies to the story of Anakin Skywalker.
Anakin is a man of noble stature. It was prophesied that he was the chosen one and so he was viewed in awe by all others. While he was a good man he was in no way perfect. He was cocky and self righteous. He saw himself as better and more important than all others based on the fact that he was the chosen one, providing him with skills that other Jedi could only dream of possessing.
His eventual downfall downfall was tragic but not pathetic. Although he does not die, as is common in tragedies, he is pushed to the brink of death after a duel with his old master and friend. In the duel he was defeated, and with the nature of a duel being noble his downfall is tragic but not pathetic.
The downfall which he experienced was deserved to a certain extent. It was not wholly deserved though since his only goal was to protect his love. In the process of protecting the love of his life he hurt many other innocent people. Of course killing all the Jedi was terrible but behind this act was the goal to protect his love. This in and of itself is not a malicious thing.
In the end not all is lost for him. While he did lose his wife and all of his friends and companions, his children survived. At the end of his life he is able to reconcile with his son, allowing him to gain back some of the humanity that he lost after he betrayed the Jedi. Anakin’s return to the light side at the end of the series allow people to reconnect with him. Even after all the terrible deeds that he committed as Darth Vader, when he reveals himself to Luke in the final scene there is a certain amount of pity from the audience. It is his return to humanity, in a way, after years spent as a heartless and bitter man that allows people to reconnect and care for him in his final moments of life after taking off his mask.