RotMG has a great idea that I wish more games would copy: difficulty scales with elevation. If you want to take it easy, stick to the coasts. If you want a challenge, strike inland towards the mountains (or follow a river upstream). It's a great way of intuitively expressing difficulty ranges across a sprawling world map, and I remember being disappointed the first time that I played Skyrim that it didn't seem to do the same.

For posterity, here's Amit on map generation: https://simblob.blogspot.com/2010/01/simple-map-generation.h...