I just saw the first couple of epsiodes of "Sons of Anarchy" and I am very impressed.

While I don't know how it will turn out in the long run, it starts promising. And of all shows I've seen, it is (at least from what I've seen so far) very close to The Sopranos. Heck, I already like it better than The Sopranos.

I haven't seen this series yet, but it looks intriguing to me, and the wife and I are looking to pick it up sooner or later:

Brotherhood.

I'll also add another vote for Deadwood. Fucking brilliant show, and one of our favorites. And although it's not at all gangster related, check out Rome and see if it's something your father might like as well. It, too, is an awesome (though short-lived) series.