Indeed. I can't imagine how these murderous greedy bloodsuckers could be honorable.
They difference I see with regular gangs, is that the Mafia is more organized and just bigger. It's a billion dollar illegal criminal entreprise, parasiting on society, stealing the money of pther criminals and of hardworking people.

I admit there may be rules from which one could derive that the Mafia is more honourable than gangs, like 'Don't sleep with the wife of another made man', and many more. But the most important rule is an unwritten one: follow and break when it turns out the best for you.