The definition of a "mob" or "organized crime" film gets kind of vague in places, I usually rule out movies where the characters are robbers of some sort or are just drug dealers, but according to your definition, I'll include those, considering that is technically organized crime.

1. The Godfather Part II (1974)
2. The Godfather (1972)
3. Goodfellas (1990)
4. Pulp Fiction (1994)
5. Reservoir Dogs (1992)
6. Heat (1995)
7. Casino (1995)
8. Traffic (2000)
9. Miller’s Crossing (1990)
10. Ocean’s 11 (2001)

If you want to say straight up "mob" films, not including drug dealer/bank robber films, then it'd be the following...

1. The Godfather Part II (1974)
2. The Godfather (1972)
3. Goodfellas (1990)
4. Casino (1995)
5. Miller’s Crossing (1990)
6. Carlito’s Way (1993)
7. Sexy Beast (2000)
8. Dinner Rush (2000)
9. Snatch (2000)
10. Bugsy (1991)

I have what I just call the top "gangster" films, in chronological order.

Top Gangster Films of the Past 35 Years
Layer Cake (2005)
Made (2001)
Dinner Rush (2000)
Gangster No. 1 (2000)
Snatch (2000)
Analyze This (1999)
The Limey (1999)
Donnie Brasco (1997)
Jackie Brown (1997)
Casino (1995)
Get Shorty (1995)
Pulp Fiction (1994)
Carlito’s Way (1993)
A Bronx Tale (1993)
Bugsy (1991)
Goodfellas (1990)
Miller’s Crossing (1990)
The Godfather Part III (1990)
Scarface (1983)
The Godfather Part II (1974)
The Godfather (1972)

too many lists.

Also, to Don Capili, not to insult you or anything, but I can't believe you liked Hoodlum, I thought that movie was SO bad.