Warning: spoilers and explanations

The movie was indeed a closure of star wars saga. A lot of people said the acting was terrible, it was dry and other things that they want to say, but hey its a popcorn movie and it doesn't matter what they say because all you need to do is enjoy the movie. The following are broken down to give further explanations: 1.) During the Clone Wars, General Grievious was trained by Count Dooku and he collect lightsabers as trophies when he killed them. In the movie, he was not as menacing in the cartoon series. 2.) Count Dooku is Darth Tyranus who authorized the Jango Fett clones in Kamino with the direct supervision of Palpatine that is why Execution Order 66 was initialized. 3.) Owen Lars wanted Threepio memory wipe in EP4 since he knows that the droid used to work for him in EP2 and might reveal secrets to Luke. 4.) The movie never actually killed all Jedi (except Yoda & Kenobi) and others like Gen Kenobi may in fact be in hiding. (Which open the possibility of exploring other stories in the future...) 5.) All droids were deactivated that is why you wont see any battle droids in the EP4. 6.) It never explained the story of Boba Fett which became a well known bounty hunter. In short, enjoy the movie and forget other critics who said the movie is bad since it is really good and entertaining.