What donnie brasco has in common with goodfellas is that its both based on a true story.It depends really. Goodfellas has better characters imo. Casino is probably more well written.
The best Mob movie is Donnie Brasco for a lot of reasons though. Well... I shouldn´t say "the best" but the most realistic and authentic on that life.
I also think pacino’s performance in donnie brasco is very good