Ebert's review seems rather cynical. Ten years ago he liked what Scream was offering up, he rated the first three films highly. I don't see anything in his review that necessarily contradicts what he said about the others. Perhaps he's just rating it low because it's the fourth installment in the series. He never really rates any fourth installment that highly anyways.
Surely, it can't be any worse than the 3rd one. The first two really good, but, IMHO, the 3rd one lost it's way
One Day I hope to be the Man my Cat thinks I am
Where are we going? And why are we in this Handbasket?