The Killing Joke
I don't care that it's happening, it shouldn't be adapted.
Batman: HUSH
The character of HUSH is interesting, but a straight up adaption of that arc won't be a good idea.
The Dark Phoenix Saga
It's kinda been adapted, but in a better way.
I don't want to see the freaking alien connection to the X-Men on film, that connection is dumb.
If you enter this thread Bamannerism, I know how you will reply, I memorized it when you said it before. Sorry dude.
Flashpoint
I don't know how the first one with Wally West was done, it was a side story, a mini series or a one shot, one I have not read. I know the second one is pretty bad, I enjoy it, but it's bad, it should not be adapted, never again after that animated film that improved the fight between Barry and Thawne.
Anything written by Grant Morrison.
Everything Ms. Marvel, BatsDC, OcStat, and daddydivine mentioned.
Dude, that's harsh ! Dark Phoenix is the greatest X-Men story ever, if not one of the greatest comic book stories of all time - I can't see how you would adapt it without the alien angle - especially since the MCU has done a great job of (mock) space opera with Guardians of the Galaxy.
I'm hopeful that it could be adapted, but it would need to be done properly, possibly over 2 movies or a TV series. You need to really build up the audience's sympathy for Scott and Jean - I mean, basing the series around Logan and Jean's romance was a terrible disservice to the fans.
I did like the death of Professor X, from Last Stand, but that was about it.
As for Grant Morrison - possibly the one thing that could be adapted is All-Star Superman, the animated version is pretty good, and it definitely is the greatest Superman story.
Also, Morrison wrote a great one-off back in 1999 "Earth 2" probably the best JLA/Crime Syndicate story ever, wayyy better than Forever Evil. That would totally work as an animated film, or a live action JL film.
(BTW they already adapted Morrison's the Invisibles.....except it was called The Matrix)
I agree that they should not adapt any of the Crisis stuff - except the original Crisis on Infinite Earths (that was awesome) but the other crises kind of sucked.
As for Batman..... well Nolan incorporated a lot of Long Halloween into his Dark Knight films, as well as snippets of Batman Year One and Knightfall.
Sadly, Snyder botched an adaptation-rip off of Dark Knight Returns ( god let's hope he never goes near Dark Knight STrikes again, which is awful to begin with).
I think Sinestro War would work, if highly modified !
Okay, sorry, those are things that could be adapted what do I think shouldn't be adapted hmmm.........
okay, okay, Emerald Twilight - because turning Hal Jordan into a villain would only have worked if they had a convincing GL to replace him....which they didn't.
Oh man, all I can think of is stuff that should be adapted, sorry
like the 1985 Secret Wars, Kingdom Come, Justice.....ahhhhhh !
Okay, I'll get back to this later.