My views are this.
Godfather: It's all about the true psychology how the Mafia worked. No one needed to be killed, but all business was on the downlow. Vito was a wise Don, knowing how the expanding Drug racket would get him more money, but knew it came with a whole slew of problems. The picture of the poster is true, the hand pulling the strings. When it came time to kill somebody, it had to be done, because no other options were available.
Scarface: All about the excess of a drug dealer who made it big, but his cocaine habit caused his downfall. He wanted it all, and when it came time to killing for Sosa, he refused to do it; screwing over Sosa.
Goodfellas: Probably the most trill mob movie ever. It showed how the Mafia worked, once again by keeping your mouth shut. Also it showed how you should never lose your cool, and respect the cops; because you can buy them. Joe Pesci's character was a good example why you should always keep a cool head. He killed a made man before he was made, which was a huge sign of disrespect. So for him to get executed from behind was not just classic, but it went to show that if you disrespected somebody, you get it right back.