1) It felt more like an extended TV Show, not an actual full length movie
2) They went overboard with the ideas for the "war" which lacked actual dragons.
3) They tried to make the giant serpent TRY to eat them but still fail, even if they're right there on a silver platter for him, he even threw a car at them, stopping them in their tracks and he lets them go on foot.
4) The marines were cowards in the movie, ran in the cave and ran out while the police in the town stayed and fought until the last minute before they died.
5) Either it was technical problems of the theatre or the audio was screwed up.
6) The actors weren't able to bring you into the mood.
7) When the snake was going up the sky scraper, the outside it showed the building crumble, he was destroying it and on the inside, the windows were barely cracked and nothing really was effecting the rooms he was above.