In no particular order...
I've been saying this since 2001, WB is extremely interested in Jude Law being The Joker. People keep telling me I'm wrong, but I'm going to laugh my ass off when Jude Law gets cast as The Joker or ends up as one of the finalists.
It continues to amaze me how much some fans of the Batman mythos do not understand the Batman mythos. The 1989 Joker was incredibly in character and ripped almost right out of the comics, save for the fact that he killed the Waynes. Now, I am not going to be real pleased if The Joker is another "Scarecrow" effort. But I doubt that will happen. I am also not going to be pleased if the plot of BATMAN 2 is one of those "Jeph Loeb style" gang war stories. I am also pretty sure that's not going to happen. I imagine Joker will feature in both Batman 2 and 3, and 3 will be the "Long Halloween" style story. However, this stuff about the Joker being mysterious and striking from the shadows some of you keep piping...go read a comic book and give me a break. The Joker sees and dresses himself as a killer clown. That's one reason he essentially named himself via the calling cards. I don't mind if only his presence is felt for a while, but then his PRESENCE needs to be felt. I don't mind if he's a bit more realistic (I.E, a man who actually wears makeup and dyes his hair as he was in my incomplete Batman 3 script), but he needs to be IN CHARACTER.
I'm not sure why MASK OF THE PHANTASM is even being brought up. That's one of the worst usages of The Joker I've ever seen. And he was hardly mysterious in that. He was quite flamboyant, actually.
And Kevin Spacey's Lex Luthor does not have a small amount of screentime in SUPERMAN RETURNS. I'm told he has about as much screentime as Magneto had in X-MEN. He's a very large part of the movie.
In conclusion, Chris Nolan and David Goyer brought us an 80's Batman without the camp. Nolan is a huge fan of that era of the Batman comics. Ten bucks we're going to see an 80's style Joker without the camp.