Okay, here's what I think...
I really loved the first one...I thought it was clever and funny and all that good stuff! And I personally liked the second one, if only for the 2 facts that 1. I ended up having like 10 inside jokes from it and 2. I love Christopher Masterson!!!!
I saw the third movie very warily...I knew that the Wayans brothers weren't a part of it anymore, so I was scared that it would be crap! And a lot of people ended up really liking it, but I hated it!!! It was nothing at all like the first two!!! There was no connection to the others except 2 of the characters!!!! Once the Wayans were gone, the great edge that they had in the first 2 went as well!
I really don't think there should be a fourth!!! I mean, I'll probably go see it...but I won't like it or buy it or anything!!! I think one of the reasons people liked the first one was b/c they said there would NOT be a sequel...and now there are like 30 of them! It's ridiculous!!!! It's time for the Scary Movie saga to end!!!!!