Fantasy Topography

Pretty much anyone doodling on a piece of paper can come up with something resembling a map.  Making it seem plausible, on the other hand, can be incredibly difficult.  Wind, rain, continental drift and the abundance of natural resources all affect the way a world looks in incredibly complex ways.  That said, it's rather amusing to find fantasy maps that fail to account for basic considerations like water always flowing downhill.  In order to take pressure off the creator's shoulders, simple tricks like flipping a map of Ireland over or using a poorly know location (like Antarctica after massive global warming) are used.  George R.R. Martin is guilty of the former while Final Fantasy games feature the latter.

It's also worth noting that the world is a big place.  The numerous single bio-dome planets in Star Wars feel a bit excessive when you consider that all the locations featured in the six films would comfortably fit in half a hemisphere of the Earth.  On occasion other sci-fi settings will try to impress with similarly massive scales.  At best though it's a deceptive illusion that doesn't hold up to scrutiny.  Most of the planets in the Battletech universe have the same plants and animals on them.  Meanwhile, Mass Effect never lets players explore more than a tiny fraction of the various places that are available.  To a lesser extent Destiny suffers from a similar problem, but at least in Bunjie's case they development team had the foresight to realize that entire solar system is more that sufficient in terms of size for the game and any future expansions.

In my mind it's really the micro, rather than macro, that impresses the most.  The world generation and simulation in titles like Dwarf Fortress is far more localized in practice, but still an impressive feat of programming from a design standpoint.  Perhaps the upcoming indie title No Man's Sky can bridge the gap to some degree.  In order to make each world feel unique in a procedurally generated galaxy players will need to be able to modify the terrain.  If you think of all things people have built in Minecraft, all the creatures they created in Spore, or all the geological events they triggered in From Dust, then it would be truly jaw-dropping to see all the things players can come up with in one game space.  Sure it might sound like mind boggling pie-in-the-sky amounts of stuff, but it's really not that big compared to the vastness of world we all live on right now.