Sometimes a movies does everything it says on the tin.
Take Peter Jackson's Lord of the Rings trilogy, for instance. It adapted JRR Tolkien's literary saga as faithfully as possible and kept surprise deviations to a minimum.
And that's all perfectly fine. The fans were expecting to see an epic fantasy adventure with large-scale battles, a ring-shaped McGuffin and a few Hobbits here and there, and that's exactly what Jackson delivered.
There are, however, those occasions when movies end up being two and a half hours of WTF. Times when the universe's collective expectations were way off the mark.
Sometimes this is great - a case of cinematic underdog defying the odds and reaching a level of excellence nobody thought possible, but often the reverse is true.
The films which end up nothing like fans were anticipating are usually botched adaptations or tonal misfires, the kind of abominations that twist beloved characters into unrecognisable husks, and water franchises down to the point where their essence has been drowned and the fanbase has taken up torches and pitchforks.