A lot of people compare this game to GTA IV. Yes both games are sandbox types in a large city, but where GTA IV has a more realistic feel, SR2 has more options in a number of areas and IMO is a lot more enjoyable.
The story takes you through the process of bringing the 3rd street saints out of obscurity and back to being the top gang in Stillwater. Fighting off the attentions of 3 other gangs, the local plod and the Ultor corporation.
Graphics are decent but not stellar, character animation is good and the amount of options open to you in pretty much every category is excellent. The game has a very good sense of humour and the learning curve is acceptable. What's more, you can customise pretty much everything from your characters hair-do to the stripper pole that you install in your cribs.
The missions are varied and there are a large number of side diversions that once completed reward you with a number of unlockable bonuses, for example complete one of the diversions at the airport and you get a Pimp Cane that doubles as a shotgun with a 16 round magazine. You can also buy the stores in the areas that you control for a discount on their merchandise, each store you buy also pays you a set amount of money each day. Which comes in handy for furthering your reign of terror.
There are a few bugs in the game that I've found, for example pimp out a number of cars one after another and return them to your garage and you'll be able to see the knee-cappers from previous rides still on screen and the still pictures when you load the game still show the original character, no matter how much you customised him earlier. However, these are minor and don't detract much from the game.
Altogether SR2 is well worth your money, this title should be in the collection of every gamer.