For me, gameplay needs to come first, and it's not necessarily an issue of the gameplay being good or bad. If I can't enjoy it as a game, it's very difficult (and so far, impossible) for me to proceed as much as I like the story.
The closest example of a game where I liked the characters and story but didn't like the gameplay but still finished the game? Devil Survivor. I suppose Planescape and Baldur's Gate II goes in here too.
The list of games with possibly legendary story/gameplay that I never finished or even got far because of my dislike of the gameplay is probably longer but the ones that come to mind most easily are Final Fantasy Tactics, Jeanne D'Arc, Mass Effect and KOTOR1. I'm still trying to decide whether I'm willing to step in for Portal at the moment.
The closest example of a game where I liked the characters and story but didn't like the gameplay but still finished the game? Devil Survivor. I suppose Planescape and Baldur's Gate II goes in here too.
The list of games with possibly legendary story/gameplay that I never finished or even got far because of my dislike of the gameplay is probably longer but the ones that come to mind most easily are Final Fantasy Tactics, Jeanne D'Arc, Mass Effect and KOTOR1. I'm still trying to decide whether I'm willing to step in for Portal at the moment.