If you buy games to be entertained, then Saints Row 2 is better than any GTA game thus far.
Hilarious characters & story, awesome character customisation (I made an emaciated dual-revolver-wielding heavily-tattooed mime-face with bright blue hair) it doesn't take itself seriously (but doesn't get so stupid as to be annoying), has more varied gameplay than the GTA games, and oh, by the way, HAS CO-OP.
THE WHOLE DAMN GAME can be played with your friend right next to you. Running over pedestrians, breaking police officers necks... together. So damn fun.
Get it.