No the Empire was created by Sith, because Sith need an army to conquer the galaxy for there own self-centered and egotistical ends.
If there was no Sith there would be no Empire.
The Empire is just a tool, a weapon to for one man to get his way.
... If this were a normal Empire, maybe. But this is a Sith Empire.
Thing is - the Sith are a ruling class, they are using the Empire to achieve their goals, sure. However, the Empire is not Sith. Just look at our average politician - you'd think your very own country is a tool for liars and hypocrites to become richer and to spread their economical and political influence beyond the borders of their country.
The backbone of the Empire are regular people. The game shows them as proud, sometimes arrogant, but also patriotic, loyal and brave. To me (and my grey Sith character) those people are the Empire, not the paranoid crooks who plot against eachother in dark tombs.