I think single issue forks should be presented in the Fork overview in a special way (for instance with the linked issue), but I was mostly talking about actively developed forks which are hundreds of commits further than the original project/upstream. Github should be doing more to advertise these for instance by showing the top 5 forks in terms of activity.

Also too many forks are just user interface mistakes where somebody wants to look at the lists of forks but accidentally forks the projects by clicking on the Fork counter in the top right corner rather than the Fork counter in the "About" box of the project.