First off I just want to say this is a very detailed game and even though the game world isn't as big as GTA4 or other open world games the amount of detail makes up for its size.
What's great: Story - great storyline you actually feel like a 40s mobster
Movement and gunplay - to me it's much easier to move and more fun to get around than in gta 4, not bashing gta4 just my opinion, gunplay is a huge part of the game and is done very well
Robbing stores - very fun (and profitable) and everytime you rob one if you go back a little later it will be closed with caution tape everywhere as if it was under investigation.
Bribing the cops - extremely fun to do if you hold up in a gun store and then after you've killed a bunch pickup the phone and pay them $500 to leave you alone.
Detail - every aspect of the game is incredible detailed, just the little things like your suit and car getting dirty after use makes the game feel alot more real and the dynamic clothes so your tie will blow in the wind along with the end of your raincoat.
What's not so great: Ending - not going to spoil but to me it was a really big cliffhanger
Poor replay value - To me there really is 0 replay value since once you beat the game that's pretty much it and with no way to replay any of the chapters makes the replay value even lower.
Cops: Very annoying, they seem to be everywhere it's not super bad since if you commit a petty crime then they just fine you $50 or you kill them and then change your clothes.
So to me it's a great rent, really enjoyed it but by no means is it a buy, if there was a way to replay chapters or more end game content then it may be a buy but still a great game.
I need to give the game it's due for graphics, sound and a decent storyline. I am very surprised at the high ratings for this game though. It is a rather quick single player game (8-10 hours) with no multiplayer and no replay value. The only reason you would replay it is if you were going for 1,000 gamer score. The majority of the achievements are fairly easy to get. I do have to say that the Playboy Magazine collectibles were a great idea.
This game is focused only on the chapter missions-no side quests really to speak of. You can steal some cars for cash and do some stick-ups at the businesses but other then that no dice.
The game is an excellent rental but a definite pass for purchase.