Well, actually, it's not strange at all the you would find these characters repellent, because that's exactly the purpose of these movies. Godfellas is supposed to be a deconstruction, that is, a movie that shows how the life of criminals, which is sometimes glamorized, is really awful and full of blood, paranoia, misery and betrayal. Ironically, Godfellas is based of the lifes of true criminals and those were actually very very worse than their depictions (that's usually true for most of these movies, ditto for Departed and Black Mass, which are based on the same real life events). However, the movie was so well received that actual gangsters (including the real Henry Hill, who was interpreted by Ray Liotta) found it flattering, missing completely the point.