Adding something for the controller doesn't make it mandatory for the keyboard and mouse, unless you specifically choose to develop for the lowest common denominator (make the game fit the controller, rather than vise versa). [/quote]

Yeah, but that's pretty much what you have to do in order to make it work for the controller. The lowest common denominator. Unless there are two different UIs, one for the limited controller options and one for the PC.

The other factor is voice acting. Do you really expect the same richness in dialogue options and story if every line has to be voiced? Everything the PCs and NPCs have to say?