It's hard to answer this question so broadly. It really depends on the RPG, but I strongly prefer if both options in the poll were at their best when I am playing one.

That being said there have been times where I felt that the gameplay and story/characters held my interest enough to play through an entire game.

Example: I always felt that FFX-2 is a bit disjointed, but I love the game's version of the job system enough to play through the whole game.