The Batman vs. Superman, although not really knowing a lot about it, seemed and seems the most interesting, most potential to be both good and successful, make sense as follow-up with older, more experienced Batman regardless of if with the Joker it's really in same continuity.
I like Scarecrow a lot but Schumacher's version for 5, especially if he would be played by Howard Stern, seems like he would be at best too much like movie Riddler again and the idea for Harley Quinn as Joker's daughter (seeking revenge, 10 years later) seemed really lacking, very INO and just doing her for being out of other/better ideas, and Aronofsky's Year One kind of interesting but a little too different and in some ways different for sake of different.