Well, we've got procedural, landscape generation, (TG2 is but one of several each with their own distinctive feature set), theres a number of tree generation systems, (mostly variants of L-systems) and I've seen a few facial and human body modeling programs that use a genetic variation to make up different characters. The trouble with all these systems is twofold, firstly that the system has to be "taught" in some manner what results are acceptable and secondly that they all work on a trial and error approach. If you hit the random seed button enough times your bound to come up with something interesting. I'd like to see a system where I could "rough" our a basic landscape, tree, body shape etc telling the program that I want a mountain, valley, tree limb or body part in a certain place and the fractal/procedural detailing would take over from there. I think the latest iteration of World Machine allows you to map out mountain ridges (haven't updated in a while so I could be way off) and this would be a step in the right direction. Another option I would like to see is "fractal isolation" and blending where I could grab a feature from one procedurally generated landscape and use in in another. I think we're a way off fully procedural modeling but we're on the way.
Richard