All four movies you mentioned have been the subject of many threads here, Meggie, including dialog games. They just haven't been mentioned as often as "Goodfellas" and "Scarface."
My subjective opinion is that "Casino" is the best because it's a very carefully made, in-depth movie with excellent performances by DeNiro and Pesci, an awesome performance by Sharon Stone, and the usual Scorsese brilliance. But it's a notch below "Goodfellas." "Donnie Brasco" is a fine film, but the book was vastly better. I didn't much c`are for the other two.