Can't stop playing it, there're just so many things to do!
The game begins when your character wakes up from a coma in the prison. Then you gets to customise your character.
The customisation is the most in-depth I've seen in video games, you could make almost anyone you want, the option is almost limitless, this is actually one of the best feature in Saints Row 2. You could play as either female or male, and yes, it's one of very few open games where you gets to play as female. You could make your character a muscular bad-ass or a skinny gangster wannabe, or even a fat tough looking clown, while making your character fatter or more muscular doesn't mean he/she gets bigger but your character will actually looks fat or full of muscle like in real life. The facial customisation is very detail, you could add make-up for the character as you like as each kind of make-up will open more option to make your character looks as you want him/her to look. There're great number of hairstyles available for you at start, and you could also customise your character's hair colour with 2 primary and secondary colours. Other than that, you can customise character's voice (with 3 male, 3 female voices, each with different lines), your character's fighting style, facial expression, walking style, taunts... Later in the game, you could customise your cribs, gang's style, your gang's car and buy new clothes, tattoos, jewelries.
The world in Saints Row 2 is pretty huge (150% bigger than the original), as you have the world open from the beginning with no invisible walls anywhere. You could travel from this end of the city to the other without a single loading scene. The world is dynamic, full of different NPCs, sometimes you could catch a couple sitting on each others' laps, people reading newspaper, a skater falls over on the sidewalk, ...etc. people reacts as you progress through the game (for example you are playing a Ronin mission, people could come to you and tell you how they don't like them and wish for you to get rid of them)
The gameplay is as great as ever, the game is over-the-top with SO many things to do. With diversions you could perform them anywhere on the maps like Taxi diversion where you take over a taxi business, Car surfing where you balance yourself on top of a car, hold-up where you robs stores and so many more... to get both respect and money. And all the great activities like Insurance Fraud, Mayhem, Demolition Derby, Drug Trafficking... are coming back from SR1 adjusted so it's much more enjoyable, there're new ones as well like Septic Avenger where you spray human waste on property, Fight Club, Trail Blazing, Crowd Control... The Missions, Stronghold are also very well-designed, to give you as much fun as possible, they don't ever feel repetitive.
When you're tired, you could get back to your crib and enjoy a video game on your TV - Zombie Uprising.
The graphic is good, Saints Row 2 is not an ugly game, occasionally the graphic's pretty great, the main characters are full of detail. There're tons of popular music in Saints Row 2, divided into different genre, if you want to listen to what you like, you could always buy a song in music store and add it into your playlist.
There're plenty of glitches, but they don't effect the game very much, the difficulty is just right, there're checkpoints throughout the missions and a new auto-save so you won't find it very frustrating. Activities are somewhat hard at level 5-6 but very rewarding.
The replayable value is indeed very high, with so many things to do I couldn't get tired of the game. The game is great, and a real joy to play, I couldn't recommend it highly enough. 10/10