As nokkon said, it all boils down to the game. Certain games are lovely on kb/mouse, others are plain arkward on them and would be better suited to a pad. It really is individual games, within the genre of RPGs some are better with the use of a mouse, the likes of neverwinter nights, while otheres are obviously oriented to the pad side, the likes of final fantasy etc.
I gamed using only WASD and mouse for about two years until the 360 was released, and while i sucked at first, i soon got better.