There is a difference between a "Storydriven" RPG and a "Non-linear" RPG.
Storydriven RPGs encompass the Final Fantasies (good until ten and ten-two <img src="/ubbthreads/images/graemlins/puppyeyes.gif" alt="" /> ), infinity engine games (BG2, etc) and even Divine Divinity.
Non-linear RPGs encompass many Muds, some MMORPGs and (from what I have seen) the Wizardry games.
To say that one is the "true" RPG really does a disservice to the other genre. ROLE PLAYING GAMES force you to take a role, even if that role is plotted out in advance. One can make the argument that some "non-linear" RPGs arent true RPGs because you can play the game as yourself, and not as a different type of character.
I am personally a fan of console-type Storydriven RPGs, simply because I dont have the self-motivation to really do everything without guidance <img src="/ubbthreads/images/graemlins/biggrin.gif" alt="" />
