I trust Leto to pull off Joker in his own way, but that's also because the Joker is a character who can be played so many different ways effectively. The original Joker, to Nicholson's over the top, to the Animated Seriesvarius versions (black reggae Joker aside), to Ledger's dark and enigmatic one are all so different yet work amazingly well. I'm not happy with his look, but at the same time, for this day and age, it does come off as crazy/psychotic as good or better than just clown makeup, especially with them seemingly going for the white skin period not makeup look.
Luthor has been essentially the same in almost all mediums though, not sure I'm gonna be able to buy him as a gang lord or whatever they've done with him.
If Eisenburg makes it work though... We may have one of the best acting jobs in a movie in a long time.