An ambitious take on a classic film set in an open world!
Your goals are simple, take over as much territory, rackets and shake down as many businesses for protection as possible. There is a basic story element behind all these things that doesn't get in the way and you can easily switch between the story and side missions. Once you've taken over as much as you can you can find misc items and weapon upgrades throughout the massive map. But there is very little left after you've accomplished everything left to do other than sit around and collect cash. The game offers a good while of missions and things to do but after that it's a shelf decoration.
I couldn't compare this game to GTA but it does borrow elements and brings a whole new light to the open ended, open world genre. I can't speak on how closely it follows the movie but the game as a stand alone is great for the price. If you haven't tried it yet, get on it now!