Characters or Story?

[Primus Inter Pares]

Neither as as important to me as world-building and atmosphere.

Oh this is a good point, if we consider world-building as separate from the Story/Plot then good Characters, especially a good villain, are definitely more important than a good story. However the world-building is really what makes or breaks any RPG, other genres need good gameplay but RPGs need a compelling world to want to spend time in.