I'm talking about Sith infighting, which is what the Rule of Two got rid of. Sure some of the other Sith Empires lasted longer than the Galactic Empire, but none of them were able to accomplish what Sidious did. That is what makes the Rule of Two great. Darth Sidious was able to do what no other Sith could do. To say that the Rule of Two is 'weak' or 'dumb' is wrong.
As to your other point. You think other Sith Empires would have no rebellions? Galactic History begs to differ.
sure but they lasted and prospered for milenia, the GE not even 20 years lasted.
You could say that sidious were able to get revenge that the sith long wanted, but thats about it. Imo he achieved that. In practical terms the sith empires of old were much more.
They achivied other kind of things, mainly projecting way of lifes when the dark side was supreme, they created a world/ society where sith lords were part of the ruling elite, and made it work, things were only bad when they chose to confront the republic if you think about it.
There were infights, yet they conquered worlds and prosper alot. What that says? while the sith empire can take a rebelion and get on top, the GE cant because there are only 2 sith.