Excellent Cadavers with Palminteri was a movie which I saw by the name of Falcone, based upon the real story of judge Falcone in Sicily in the 80's, who got killed.

By the way, you can hardly call such films as A Simple Plan and Out of Sight real gangster movies, or Se7en. Neither is Memento, which is a brilliant film, but it's more like a mystery.
If Se7en is accounted for, then you can mention all other Morgan Freeman-detective-like-thrillers and all Hannibal movies and all... you know what I mean.

You might also want to consider two similar movies about John Gotti: Witness to the mob (1998) with Tom Sizemore as John Gotti, Richard Bright and Abe Vigoda, a Robert De Niro production for TV about a 'buttonman' of Gotti (Nick Turturro), and "GOTTI" with Armand Assante as John Gotti.

These are the Imdb plot-summaries online:

Excellent Cadavers/Falcone:
Fact based story about the political battle that was waged against the Mafia in Sicily during the late 1980's and early 1990's. Chazz Palminteri plays Giovanni Falcone, a crusading prosecutor who tried to use money trails as a way to attack the mobsters. He is aided by a former mobster (F. Murray Abraham) who volunteers to turn state's evidence after his sons are killed by a renegade mob chief. With the mobster's help, the prosecutor was able to obtain over 300 convictions before he was assassinated in a bombing in 1992.

Gotti:
John Gotti, the head of a small New York mafia crew breaks a few of the old family rules. He rises to become the head of the Gambino family and the most well-known mafia boss in America. He is known as the Dapper Don for his expensive taste in suits, and the Teflon Don because none of the FBI charges against him will stick. Life is good, but suspicion creeps in, and greed, rule-breaking and his high public profile all threaten to topple him
Both movies star Frank Vincent, but in different roles I believe.
By the way, Gotti died this year in New York.