I came accross World Machine, a Terrain Generating software, and somehow, I got the Professional Version. I made this mountain with it. It looks simple, but I needed an hour to make the mountain in World Machine, and then another 15 minutes to make it look nice in Blender. It also tired my PC with its over 2,600,000 polygons.
Yes... I was extremely disappoitned when I saw that the extra polys gave no detail. BTW, this terrain is 16km wide and long and about 3km high. I wanted to work real scale, but I would need to make the texture 16k pixels(yes, possible) instead of 4096. But It took me long enough to make it at the present, so not talking about 16 times greater resolution.
2.6 million polys... still not 'that' impressive...
By 'that' I mean something like this (not by me)... dl.dropboxusercontent.com/s/zal4fzvugnkbavx/DesertLandscape.jpg?dl=0 This was made by a person with username Hokiroya. You can find him/her (yes, I don't know the gender) on Blender artists and YouTube. This was made in just vanilla Blender. No additional software/addon used. Time used : 3-4 hours(no kidding)