A Mafia II Review for you:
I just completed Mafia II. It took 11 hours (on hard difficulty) which is longer than the Modern Warfare games were so I don't really get why people are complaining that it's too short. I think it is very easy to compare it to GTAIV, if you have the attention span of a gnat that is and you expect a slurry of sidequests to be presented to you to make your £30 worthwhile. The first Mafia was only a semi-open world game and the sequel is very similar in execution. The flow of the story is uninterrupted, very linear and goals are not missions - they are chapters.
Comparing it to it's predecessor I see a worthy sequel, a general step up in all areas that made the first one great. The visuals are amazing, I can run it on full settings on my (Core i3/GT 330M/4GB RAM) laptop at the native res of my screen (1366x768) so it is pretty well optimised also.
The acting is the best acting in a game that I have seen so far. You can really empathise with the characters to the same level that you would in a Mafia film in the cinema. There's a lot of mob humour and some time-period-excusable casual racism thrown in for good measure. The plot is fairly stereotypical of a Mafia-style game, it's just done in a no-expenses-spared kinda way which is what makes it the gaming equivalent of a page-turner.
The gameplay is really well rounded with a more fluid cover system than GTA or Gears of War. There's no feeling that a level was designed to accommodate chest-high walls at any point in the game. Just because you're in cover doesn't necessarily mean you're bullet proof either as the edges of pillars and corners of walls can be chipped away by enemy fire. The chapter locations and level design are exceptional.
In the first Mafia the cars were designed so that they ran at a speed accurate to the time period. For example, for the whole first act of the game you couldn't drive over thirty miles per hour and it was difficult driving up steep inclines. For the gamer that enjoys a ninety MPH chase around the a city this was probably agony but I liked it! Back then 2K had the balls to put slow cars in their game and for me it added to the authenticity and character. This iteration features a lot of driving but the cars all run at acceptable speeds. There is a lot of driving in the game and there are no journey-skip options available. Mafia II doesn't have a quicksave feature and the checkpoints are not as regular as some people would wish. I think we take quicksave for granted in a lot of games and you don't necessarily have to be as skilled to get through a level as the number of challenges faced are less cumulative. The point I am trying to make here is that Mafia has always been the patient man's GTA. It's more immersive and that's the way I prefer it.
"But there's no multiplayer?" - The consumer's desire for multiplayer is something that detracts from the overall quality of a game in my opinion. I completed Uncharted 2 and traded it in for Modern Warfare 2 when it came out. I played the single player campaign of both and never picked them up again afterwards. I have completed the first Mafia game three times since I bought it in the bargain bin two years after it was initially released. I imagine that I will do the same for the sequel as it is excellent.
In summary, buy Mafia II if you have an attention span and a desire for a good story-driven game you can play time and again. Do not buy Mafia II if you expect it to be completely open-world and nonlinear, because it's the opposite.