I need help writing a simple plot in a Fantasy world

Hi there it's Cybrim, I'm trying to come up with a story, but this is a short one with an optional quest and the actual quest. I would like to come up with an easy to understand plot like Dragon Warrior, "Princess is kidnapped, (option to save her), Kill the Dragonlord." something like this, but not this. I want a simple story that people can grasp, that I can relate to the world it takes place in, where NPCs from all over talk about these horrible things and Dragon Warrior does this well.

The Goal:

To have a simple story to tell that hasn't been told too much (kidnapped princess, dang Mario you have a bad sense of direction, I mean thanks for saving me from that guy but wow I think you really like me bro- Toad).

The Plan:

To have side stories that are the more complex side of the overall story (Mass Effect, Dragon Age).

The Vision:

To create a "Campaign Setting" with many hidden quests and other things that you would have to find by exploring the world and helping it's people (Persona).

The Problem:

Writer's Block.

The Assets:

A ton of RPG Supplements, gameplay experience, the idea... and hopefully you guys.

I don't want to solve all of  this world's problems, Campaign Settings are places and times with initial problems that no single group of heroes could ever hope to solve in their lifetimes. I don't want the players to think of it as a normal game.

OK, a spin on a common story:

Hundreds of years ago, a dragon destroyed his kingdom, and the noble Lord X died in the climactic battle.  He doesn't remember much, but recently he felt a force dragging him from...somewhere...back to this world.  When he woke, he found he had come back as a (Lich/Vampire/whatever).  And he remembered why he was here:

He swore to defend his kingdom, even past his death, using dark rites for a noble cause.  Now that the dragon has arisen again, so has he. 

That gives you an interesting spin on the "Kill the dragon" basic plot line.  Both are already dead.  Now what?

It sounds familiar though.. I have 8 City-states, all of which are independent of each other and it is post apocalyptic (rebuilding fantasy era), but I need a reason for the heroes to come to this side of the world or even care about it. Thanks whitesphere, any more ideas? that relate to the 8 city states maybe and the fact many people are trying to rebuild their lives after "the catastrophic event" (which needs an actual name). I already have the most simplest of ideas about the world, but I need a plot to pull the heroes.