Clearly, Sidious takes out Obi Wan (he's good...but not ready for the emperor was he). Anakin, certainly is no match for Yoda either and I think he would be to twisted for even Yoda to bring him back by now. \n\nSidious must now take on a new apprentice, but he still succeeds in creating the Empire, although weaker without the power of Vader to help him. Obi Wan isn't able to deliver Luke or watch over him, or influence him to join the rebellion. Yoda still has him transported to "his family" and after Owen and Veru are slain he joins the Academy to become a gifted pilot in the rebellion. \n\nHan is never employed by Ben to fly to Alderan, and Leia is executed by General Tarken as planned, prior to the rescue. \n\nR2D2's plans never make it to the rebellion and they are ultimately destroyed. Luke is captured by the Emperor once he realizes someone that strong in the force exists. Luke, without the influence of Ben and Yoda, is easily converted and trained in the Dark Side from scratch (probably killing off the interim apprentice). \n\nThe Sith rule for 1000 years.