I really loved QFG aswell. I haven't come across any actual adventure games like it since though unfortunately.
But in many ways IMO Gothic 1 and Gothic 2 have a lot in common with it. Its just where QFG comes at it from the 2d point and click adventure game direction, Gothic comes at it from the 3d third person, over the shoulder camera, rpg direction.
There is a demo for Gothic 1 here
http://www.3dgamers.com/games/gothic/ if you want to check it out.