When it comes to Parody flicks like Scary Movie, Airplane or Young Frankenstein, it has been hit or miss for me. I lean more toward those that are making fun of a genre like the later two than I do with Scary Movie which is more about making fun of specific movies. Why don't I like that? If I want to see the actual scenes they are ripping off, I rather just watch the original flick instead. But there are a few instances where they do nail the scene and it gives me a good laugh. But that's one scene and it usually doesn't make up the movie as a whole. Now a movie like Airplane, Naked Gun, Silent Movie, High Anxiety and Young Frankenstien, I can watch all day because even though it's a parody, what they are doing is not ripping off any one thing in particular. Okay, High Anxiety is definitely guilty in that department, cribbing a lot of Alfred  H i t c h c o c k. But it's the fact that it's Genre Parody > Movie Parody that makes it work for me on a personal level.

BTW, awesome idea for a thread! Why I didn't think of it before? Ack!

If I recall correctly, Hitch donated some ideas and guidance to High Anxiety, and Mel Brooks did the same for Hitch's current project.

I wonder if the Wikipediafication of Fine Arts (an idea I'm constantly referring back to) plays into this as well.  Back in the day, we had the same narrow pool of knowledge we all drew on, and you could turn that into parody.  Now our attention is so widespread and unique, it's hard.  The one thing we have in common is the variety, which could be why parody movies have to do as many references as possible.