http://en.wikipedia.org/wiki/Intertextual
Intertextuality is the shaping of texts' meanings by other texts. It can refer to an author’s borrowing and transformation of a prior text or to a reader’s referencing of one text in reading another.
Shakespeare has a lot of meaningful connections to earlier stories in his plays. The Tempest rips off the Faust story, but it adds a lot of new things, like for example using a female familiar spirit and no obvious devil.
Not every rip-off of Faust is as inter-textual as Shakespeare's Tempest but the potential is there.
And, granted, I want to see them rip off other anime shows, but that's a separate issue from Artefact's recent complaints about high-school tsundere love rip-offs:
http://www.sankakucomplex.com/2011/01/10/winter-2011-anime-least-original-ever-just-rehashes/
http://www.sankakucomplex.com/2011/01/14/winter-2011-revisited-now-with-even-less-originality
Personally, I want to see good rip-offs, even rip-offs that I like better than the original.
Example: Fairy Tail rips off superhero soap opera plot dynamics with minimalistic art from One Piece. But I like Fairy Tail better than One Piece.

The Empire of Corpses Gorily Grim
One Piece: Burning Blood Total Bikini Madness
Bakuon!! Wild & Rough
Milky Mimi Ero-Figure Deliciously Creamy
Dead or Alive Ero-SFM Doubly Dirty