The thing about episodic serial media is that it can establish the myth in some episodes (probably most of them) and then explore the myth in others (probably the best-known and best-beloved ones).  Knightfall and The Killing Joke and Arkham Asylum: A Serious House on Serious Earth are all super great, but they wouldn’t work if we didn’t already have a very clear understanding of Batman, and we have a very clear understanding of Batman because there have been one hojillion comics and TV episodes in which he’s doing the Basic Batman Shtick. 

If you’re trying to reboot the work in compressed form, you can’t do this. 

This creates a hideous dilemma: people will want your Very Most Iconic plotlines and characters and so forth, but odds are those things are iconic precisely because they do unusual things to the status quo, and you haven’t actually set up the status quo yet.  Superman breaking his no-killing rule means something very different if we haven’t gone through hundreds of issues of him never ever doing that.  Irene Adler outwitting Sherlock Holmes means something very different if we don’t have a cushion of three dozen stories in which no one can ever outwit Sherlock Holmes.