Hi Kronos
I've found that the L3DT serves the game developer best.
L3DT can generating artifical terrain maps and textures (height, normal, light map) developed by Aaron Torpy. There is a free standard (it is free to use commercially) and a very reasonably priced professional version.
The best thing about L3DT is that it supports several modes of operation. You can set a few general parameters and let the program do all the work, and you can also manually edit your map and use a design map.

How to create terrains using L3DT

road-making tutorial