but sadly, simply generated heightmaps & normalmaps suck. (especially the heightmaps)
well... yeah, in some cases the generation algorithms can produce decent normalmaps but making them "by hand" (you don't actually hand-paint EVERYTHING)
is still the best method.
I once made an example, guess which of these was generated

(click to view in full size)...and regarding generated displacement/heightmaps: just don't use them, please.