That's true. Sometimes I make an opinion about a movie too quickly. For instance I always taught Big Lebowski was some weird movie so I never watched it, but I eventually did and I thought it was AWESOME. I was kicking myself for not watching it sooner.
I guess I'll give it another chance since you say it's good.
--> "The only thing I don't like about that is sometimes a trailer tells you too much about a movie. I was about to see the movie Children of Men because a friend said it was good and when I looked at the trailer it basically told you the whole story of the movie and it gave you so many clues about the end. The trailer kind of ruined it for me."
That's kind of a mistake, the film narrative is amazing and you are allowing an hour and 50mintue film be summed by like a minute worth of material completely rearranged chronologically. For compositional technicality and thoroughness of the atmosphere its a jolly good watch and I would suggest you re-think your thoughts... since that's usually what rethinking something infers.