I'll tell you too, I saw Young Frankenstein when it came out and was stoked. It also got good reviews. And I was disappointed because it was really a simple parody (as is Blazing Saddles, Spaceballs, the un-remembered Hitchcock parody), The Producers is an original invention.
PS. I think my highest rated parody would be This Is Spinal Tap, but I've not watched it in years.