Star Wars - 5
The Empire Strikes Back - 5
Return of the Jedi - 5
The Phantom Menace - 5
Attack of the Clones - 4
Revenge of the Sith - 4.5 (wasn't an option so I voted 4)
The Force Awakens - 5
Compared to most other film music out there, they should all get 5s. For me, Attack of the Clones has a beautiful theme but a lot of the other music isn't as good as the rest of the franchise. While Revenge of the Sith has some great music but doesn't have any unifying theme that makes it stand apart from the rest of the franchise. Battle of the Heroes doesn't show up until the end of the score so it's not a theme for the movie as a whole. The only theme used throughout is the Force Theme but because that is used in every movie, it doesn't give Sith it's own musical identity.
Still, all of John Williams's Star Wars scores are light-years ahead of most film music out there! It's a shame none of the prequels got him an Oscar nomination because he deserved it regardless of the quality of those movies.