Best "Gangster" game was Mafia.. there supposed to be coming out with Mafia II soon, probably the start of next year.. the first one was great.
http://xbox360.ign.com/objects/957/957837.html
I wasnt feeling Saints Row 2 when i first played it. But it grew on me, its so fucking fun. The gameplay and fun factor shits on GTA4 IMO and its even better if you play with 2 players. I never get tired of it now. Just pickin up people and chuckin them, lol.. shits so funny.