Donnie Brasco, Carlito's Way, A Bronx Tale - these all to me fall into the category of fun mafia movies that have really great mob movie scenes but also aren't actually great movies. "Now youse can't leave" "fuhgeddaboutit". I think Donnie Brasco is probably the best out of these and Lefty (and Pacino's portrayal of him) is a great mob character. He may be the best combination of.... he's not much more than a piece of shit thief scumbag and yet you can empathize with his plight, living the consequence of a lifetime of being a piece of shit. It's also interesting how much of the plot is relatable to corporate drones - he's got some ambition to be more than essentially a low level manager and it's never going to happen for him, and then he's getting batted around in a power struggle at the higher levels, his golden boy protege is ripped from him, it all blows up and they're going to chuck him out with the trash.
I'm coming back around on Donnie Brasco being a good movie. It suffers from being very late 90s.
I haven't watched The Untouchables in maybe 8 years or so but I remember thinking it was not nearly as good as I remembered it. It may also be just suffering from seeming very of its time.