By selling the most? I would rather get GTA4
SR2 was .. pretty boring, stealing off SA features on the hood ownings/defending
GTA4 has pretty graphics .. if you've never been to new york... well now you can

Of course it isn't exact rip of the map but they did take NY buldings, artworks like graffiti, etc
SR2 also fails@humor and most of the guns/clothes get unlocked towards the end.. Roaming around sucks *** in this game, its a type of game where you finish the game and dont want to touch it again