Okay, This is not exactly my favorite genre, as I tend to lean more towards comedies, action, sci-fi and fantasy. I will do this because I said I would (here you go, 5020). Some of my picks I haven't seen in a while, so I will forgo my usual quotes this time.
(Again, in no particular order)
#1. Millers Crossing
#2. Scarface
#3. Goodfellas
#4. Casino
#5. Heat
#6. Carlito's Way
#7. American Me
#8. Colors
#9. New Jack City
#10. Road to Perdition
#11. Gangs of New York
#12. Layer Cake
#13. Johnny Dangerously
#14. Romper Stomper
#15. Big Money Hu$tlas
I didn't put the Godfather's because I haven't seen them. I'll probably do a "Heist movie" thread later on down the road, so movies like the "Ocean's 11/12/13", "Dead Presidents", ETC should qualify for that one.
Discuss, and have fun! :)