The Dark Side is the part of the Force fueled by emotions and passion. It is described as destructive, toppling existing laws, societal structure and hierarchy in order to strengthen its practitioner and free him from restrictions ("break chains"). At the very core of the Dark Side is the disregard for any rules except of one's will and thirst for power.
Palpatine was an ultimate Sith Master and very powerful practitioner of the Dark Side. He used it to destroy the Republic and the Jedi Order (individual Jedi remained, but they acted as individuals, not as an organization). Yet, after that, he created the Empire - very rigid, militaristic state with its own laws and hierarchy.
Question is, did he, by creating such strict government, actually weaken the Dark Side and himself, thus allowing the Light Side to recover and ultimately defeat him through the efforts of the Rebel Alliance and Luke Skywalker?
The Question is not opinion based. We have been explicitly told (by Yoda no less) , that "The dark side clouds everything" at the time of the Clone Wars. Later (in the final episodes of the Clone Wars TV show) we learned that the Jedi were partially responsible for this by participating in said war. If we assume that the Dark Side was not that powerful at the time of the Battle of Endor, the question is simply did Palpatine's action actually lift the shroud of Dark Side?