You don't like Mean Streets. That's what's the matter is. :p

Well, it's a hard question to answer without being typical and expected. You could go for the "oldies" and more boring choices such as De Niro, and the obvious ones such as the WHOLE cast of The Sopranos. David Chase has the best of everything right now; just about every noted good (American) gangster actor has signed up for The Sopranos--and that was topped off with Vincent joining for season five. Like DSS said, all of these have been typecast.

My unconventional choices that I think would be excellent in a gangster film.

Ray Winstone
Robbie Coltrane
Ian McShane
Tim Healy
Malcolm McDowell
Jimmy Nail
Phil Daniels
Christopher Eccleston
Mark Strong
...and I'd love to see Stephen Fry turn nasty as a laidback mobster, sitting at a table, cigar in hand, passing down orders to whack some poor guy.

Mick