I just watched Don't Worry, He Won't Get Far on Foot. Its about alcoholism and I am guessing it was based on a true story. It was interesting and I liked it but it lacked something. I think Phoenix is a solid actor, although I am not really a fan and I don't think I've really liked any of his performances. I think maybe if a different actor played the main character in that movie I might have liked it more. I have some concern that it will be the same with "Joker" for me.
I really liked Heath Ledger's Joker. I would have watched him in his own "Joker" movie... FWIW, I didn't know anything about Ledger and I still don't. It's the only movie I have seen him in I think. Also happens to be one of my favorite Super Hero movies... top 5 easily.