The mouse is far and away a better interface. It certainly won't work to optimum efficacity on a lap; it doesn't lend itself to lounge-room game playing.
Whether it is a show-stopper for occidental RPGs is another matter.
This assumes that console users have been given a choice between the two types of RPGs of equal quality. Not sure that has been the case.
Why do Japanese consoles have to be dominated by JRPGs? Unless it depends on the controller, which it doesn't, then there is no reason to suppose that branching stories and multiple endings with different characters can't be the norm. Unless there is another limiting factor of consoles, like hardware (RAM, GPU, etc).
Disco!