I always liked Gungrave. Its an interesting mix because the first half of it is Gangster/Noir and the second half is supernatural dystopia. I'd second (or third or whatever) Baccano but if you thought that something like Cowboy Bebop wasn't 'serial' enough, Baccano is even more of an anthology style than Bebop. Personally I prefer anthology style (I'm not a millennial, I prefer what used to be the more common style of tv) So I enjoyed CB and Baccano, but if long story arc with an end (26 episodes) is your thing, then Gungrave.