Rent it, play the game, beat it. That's all folks.
Note the could in there. The problem with the system is simple. What makes creating your own character fun is just that, creating him. The problem is that you can fill up the entire stat chart. No weakness in low street smarts, no bonus in playing as one who disdains the violence of throwing punches or gunplay, because in the end, everyone has the same stats. Full stars across the chart. The ridiculous amount of violence means you would be a fool to not fill up guns and punches first. Although once you get the ability to land head-shots, with a pistol, at a range too far for your enemies to fire back, the use of physical strength becomes a novelty of beating up random punks on the street for disrespecting you.
The gang war in the background feels more like a gang hunt. You threaten some store owner, kill a few strong-arm guards, get your money and leave. Wash and repeat. There are several larger areas which require a lot of gunplay and four big houses that are a nightmarish fight to set up a bomb which end a gang. To get 100% complete, it is required that you destroy the other gangs. While you get a breath of fresh air knowing one less gang is out to kill you. You know that the gnawing in your gut means less action. Eventually, with the destruction of the gangs, you have to go on shooting-sprees or bank-robberies to get your kicks in between trying to get the rank of Don of New York.(whose protesting when I've killed them all? Apparently Don Corleone was a dare-devil in his day if becoming Don means performing tricks in a car.)
I know I come off as very negative. Don't get me wrong, this is a great game, but a short lived one. One that you'll beat once and then see it all. I would suggest first renting it. If you really, really love it, then buy it.