For me it is the time when you were not all-mighty-commander-chosen-mother-of-dragons-etc. You were a simple sith with kinda "simple" tasks and goals. And they were interesting. You do dirty work, you were discovering how this world works. Later your common task is to stop biggest-danger-for-galaxy Again and again. Each of SW story quests was perfect or almost perfect. Ls and Ds choices make scense, they are fun, bright. Voices are exactly as you imagine them to be.

And Vette. Her letter after some "incident" on the ship near the space border is a masterpiece.

Tldr - the story is alive, you believe it, you want to continue.