I thoiught about this long and hard...
Ryoga (one of my faves!) is like Kouga... he always has this wild, wolfish air about him (and pointed teeth) he is also fighting the meain guy character to get the main girl character.
Ranma is like Inuyasha - good fighter, crappy people skills, he says hurtful things without thinking
Myoga the flea is a cross between Happosai and Genma - he runs away when in danger, and likes girls...
Miroku is more like Happosai, if not so blatantly obvious
Mousse is a little like Houjo... kinda clueless
Akane is obviously like Kagome - the temper and all... plus she pals around with the main character (which the show is named after
)
Anyone got any more?