Edward Norton is my favorite amongst those 3 actors. American History X, Rounders, Primal Fear, Fight Club...
There are obviously many more roles he's been solid in, but I thought he had outstanding performances in the above mentioned films.
Christian Bale is great as well, but his best performances (in my opinion) don't even approach Norton in American History X. I guess for some, the debate will be down to what the actors have produced in more recent years - Norton's best stuff (IMO) is about a decade (+) old now, where most of Bale's good performances have come more recently...
My favorite Leo movie is definitely Basketball Diaries. Anyone who hasn't seen it, should really check it out. Generally, I have trouble taking Leo too seriously...