Successful jokes are thin on the ground in the musty sixth installment of the once-popular parody franchise, taking aim at everything from Scream to Sinners The Scary Movie series has always depended on timing. Not necessarily in its gagcraft, which has oscillated between occasional sharp jabs and many beyond-broad blows, but in its position on the release schedule. This was especially true of the first installment, which arrived in theaters just a few months after the 2000 release of Scream 3,