Abbot Genser / HBO
Sure, he's made his living playing mostly evil-doers and his isn't exactly the face that comes to mind for "leading man," but Times TV critic Mary McNamara says "he is the Absolute Best Thing about the show," adding:
"For all its period detail and pedigree, 'Boardwalk Empire' is nothing new. It's a gangster tale, made a tiny bit fresh by its time and place, by the in-your-face presence of the temperance movement (although what promised to be a complex and interesting portrait of these women in the pilot has devolved in subsequent episodes). The acting is good, as is the writing, but most of what happens is fairly predictable.
His presence, and his performance, remind us what power and corruption actually look like most of the time, and it isn't a young Robert De Niro."