Expectations are usually higher then the delivery. Most developers, publishers, and manufacturers are quite guilty of raising expectations beyond what a game will deliver. Most of the time its just accepted that the saying is true. The concept looked better in theory then it looked in practice. Sounding good on paper is easy, because most people are not cynical enough to extrapolate the contradictions or the downside. Instead you just have general cynicism.
I do not think people are annoyed that Fable under delivered as much as they are pissed that Peter Molyneux did not live up to his reputation. You expected better of his work the last time. People were buying into the cult of personality rather then the game. The man is ambitious and has a very powerful vision.
Your not pissed, because the game was bad which it was not. You are pissed that the game wasn't sheer perfection that redefined the genre. I say if your holding the man to such a ridiculously high standard then you obviously have lofty expectations for this game.
To paraphrase an old idea. A scientific genius can be wrong one time out of a hundred and be ridiculed. A prophet could be right only once out of a hundred tries and be celebrated. Which do you think Peter Molyneux happens to be?
The title certainly looks to have the potential to be the RPG of the year. Though there is stiff competition. I am not sure Fallout 3 will be original enough to carry favor. Too Human will probably be too hardcore, and the titles out of Japan may be too traditional to demand the attention. There is a pretty strong chance it will be Fable 2 especially if the story is more innovative this time around.