Well, even though Mon'Star seems to be based (intentionally or not) on a number of somewhat corny steriotypes and clice villans, he has taken those overused motifs and made them seem utterly badass.
Yes, there have been more origional characters. Yes, Mon'star's 'kill kill kill' mentality and the reasons behind it seem somewhat haphazard. But the way I see it, Disco's storyline needs at least ONE 'kill kill kill, none of the side crap' character. So yes, I think Mon'star is doing fine. Steriotypical villian or not.
He's like disco's Jason Vorhees, for better or worse.