As much as I would like to see a third instalment in the movie series, I personally would love an animated series that follows in the footsteps of the comics. We can get the actors from the films to do the voice acting just like with those two animated films that got released back in 2006 and it would follow similarly to the comics where Hellboy goes to different countries every episode to solve whatever paranormal trouble is happening, with story arcs to serve as the actual main story.
One of the problems I would have with it is that if it did follow closely to the comics, I'm concerned that it would be chock-full of filler episodes just like what happens in the comics whenever there isn't a storyline around Hellboy's role as the harbringer of the apocalypse. Also, I hated the cartoony art style they gave the animated films and how distant it was to Mike Mignola's actual style, but to be fair, they were targeting the films towards a young audience (not children, but maybe teens) so I think a different production studio should be in charge of animating it. If any of you have seen the pilot for 'The Amazing Screw On Head' (also by Mike Mignola) or pretty much anything by Mignola, then that's what it should like in my opinion.