At a brisk 90 minutes, “Cloverfield” is too fast-paced and well-produced to completely exhaust our enthusiasm for major monster mayhem, but it doesn’t take long for the lack of story to become tiring. Like some tourist from the Midwest, once the creature stumbles into Manhattan and visits Central Park and the Empire State Building, there’s nothing left for it to do but knock around aimlessly, getting in trouble and making a mess on the sidewalks.