Controller + mouse is a great combo for FPS games, and the like. I definitely prefer playing those on the PC. RPGs, though, are typically much longer, based to some degree on exploration, don't require any precise inputs, etc. I think a controller is much more comfortable for long gaming sessions than keyboard and mouse, personally. Of course, you can connect controllers to PCs in various ways, but you typically lose the bigger screen (most people have a big tv screen and a small computer monitor).

Anyway, you can set up a comparable experience with the PC, but for the average person's setup, I prefer the console gaming experience for RPGs.