I can't actually remember the last game I finished...I think it was probably GTA: VICE CITY. And that was OLD! Since then I've bought 15 games, and haven't finished one.
I never finished Final Fantsasy VII, but MAN was there a lot to do to keep me entertained while I 'went on vacation in the game'.
I haven't finished any Final Fantasy games. I like to get halfway, leave the games for about a year then restart them. I can definitely agree with the whole "Why play if it's boring?" idea. Makes a lot of sense.
If I'm happily playing my way through GTA:SA then get to a certain point where the only mission I can do will require CJ to swim back and forth in the harbour for 2 hours before I can even attempt it, why should I even bother playing? I have better things to be doing than holding the forward key and occasionally pressing tab to see my stamina bar has gone up by 1/16th of a centimetre.
Or when I'm playing Dreamfall and am then made to wander in a circle into rooms, get keycards, continue to next room, etcetera for 15 minutes. In this situation I tend to quit and go for a run. Not exactly the best design.