DUNE: Yeah, it's really weird how people keep wanting to make Paul a hero. His story is TRAGIC, people! He turns into a DICTATOR! I've never noticed the crappiness of the writing -- could be that the ideas are so compelling to me that I ignore the prose -- though most of his other books I never made it through (The Lazarus Effect, The Jesus Incident (or something like that)). Dune is one of those rare genre books that's actually about something adults might find interesting to think about.
I think this is an overly simplistic view of Paul/Muad'Dib, Alia, and Leto II/Ghanima mythos. These people will tell you that they are dictators. They tell you that they do bad, reprehensible things. Muad'Dib and Alia began the worship, they began the refinement of the merging of state and church, whose entire mythos and coming were orchestrated by the Bene Gesserit. They halted the very wheels of their universe by threatening spice. However, you also fail to consider their enemies: the Harknonnen, the Padishah Emperor/House Corrino, the Bene Gesserit, the Tlielaxu, and CHOAM.
Muad'Dib especially empowered the Fremen, and if you'll notice the Jihad was inevitable even if Muad'DIb had tried to stop it. He says as much in Dune Messiah. Even Leto II recognized the horror of what he did. He willingly created the person who would kill him through his genetics program (which was far more sophisticated than the Bene Gesserit could even hope). And Atreides genes stayed in the population by his doing for the expressed hope that never again could a kiwsatz haderach or an Abomination or a God Emperor could use prescience to rule. As long as the genes are there, humanity will always have the chance of overthrowing whatever oppresses them.
I think that you have glossed over the Golden Path entirely. Each of these dictators taught a very harsh, hard lesson to humanity because they allowed themselves to be sheep. Never be oppressed. During much of Leto's reign and after, the common people begin machinations to free themselves, not just the wealthy powerful. Herbert makes sure that each and every institute set up in the beginning of the book falls in the end especially after God Emperor. These lessons taught by Leto, by Muad'Dib, and by Alia forced humanity to spread. Elsewise you'd have Feyd-Rautha ruling, or the Spacing Guild, or the Bene Gesserit, or even House Corrino (who would probably have been destroyed by the Harkonnens without Muad'Dib's influence).
Leto II's reign was the longest and most stabilized reign by far (3500 yrs):
When I set out to lead humankind along my Golden Path, I promised them a lesson their bones would remember. I know a profound pattern which humans deny with their words even while their actions affirm it. They say they seek security and quiet, the condition they call peace. Even as they speak, they create the seeds of turmoil and violence. If they find their quiet security, they squirm in it. How boring they find it. Look at them now. Look at what they do while I record these words. Hah! I give them enduring eons of enforced tranquility which plods on and on despite their every effort to escape into chaos. Believe me, the memory of Leto's Peace shall abide with them forever. They will seek their quiet security thereafter only with extreme caution and steadfast preparation.
And in that time there were few wars, many plots, but few out and out wars. Muad'Dib only ruled for around 12 years, and Alia for 9 years. And Paul returned to his good guy status in Children of Dune as the Preacher of Arrakeen:
This is the fallacy of power: ultimately it is effective only in an absolute, a limited universe. But the basic lesson of our relativistic universe is that things change. Any power must always meet a greater power. Paul Muad'Dib taught this lesson to the Sardaukar on the Plains of Arrakeen. His descendants have yet to learn the lesson for themselves.
In my opinion, the Dune series is a great philosophical work. You just gotta dig deep.

If we want to keep this debate going, maybe we should form a new thread and not hijack this one?