This is a pretty tough question.  Sure Goku and the rest are much better
martial artists then Ranma and company, but Ranma has the Ranma Factor(tm)
going for him.  For those that don't know, Ranma Factor(tm) is the ability
to use and improve upon any martial arts technique after seeing it in use
one or two times.  THAT is the main source of Ranma's power.

Oddly enough, that's also the source of Ifurita's (of El-Hazard) power...
kinda makes you wonder, doesn't it?  <grin>

-- Bob