I've posted before saying that I prefer Casino over Goodfellas. After having just watched Goodfellas, now I'm not so sure. Both have so many good qualities:
1) great supporting actors: Casino with Rickles, Woods, and Stone and GF with Sorvino and Bracco.
2) both have annoying wife characters: Bracco & Stone
3) both have at least 1 set of brutal killings

I guess why I'm leaning more toward GF now is the acting of Paul Sorvino. He played his character flawlessly. From the slap on the face to Henry warning Hill about not doing drugs, to the way he pronounced "sang-wiches" in prison, Sorvino was a perfect mob captain.

Both seemed to drag a little bit at the end, in Casino with Sharon Stone rampaging the cars and her house, and GF with Henry being so paranoid about the helicopter and the events of that entire day.