I agree you can't put a "running time" filter on what makes a good or bad fan edit, but with the really offensive movies (like the prequels), I think they need MAJOR re-editing to make a true fan edit (i.e. not just trimming silly stuff here and there, but major restructuring, plot-line removal, etc). Generally these things (as in the case of Attack of the Phantom) lead to significantly shorter running times.

My own work-in-progress cut of "Superman Returns" is about 20 minutes shorter, although the best compliment I got was when I screened it for friends and they said they couldn't tell what was missing.

I see that as a compliment because (to me) that means the essence of the film has been retained, the story still works and no one misses any of the previously existing "bloat."

If course this is what the ORIGINAL edit of all films should be like, but then we'd be out of a job ;-)