I don't want to get off topic with discussing XII, but XII was not inferior to XIII, in fact, quite the opposite. XII focused on gameplay, XIII focused on story. I can get a good story from watching a dvd, i want something that is actually fun to play. XIII practically plays the game for you.
Lets look at the formula. Walk in a straight line - hit pre-set encounter - beat encounter by pressing auto command - watch cutscene. Repeat.
Excuse me but that isn't a game. XII may have failed in a few places (as much as i love it, i'm well aware of the flaws) but if you wanted to finish it, you had to actually play it. Lazy smurfs today just want the game played for them