I can see, you never played the game.
It's a sandbox game, that had far more time put into the sandbox then the game.
So while there is a story you can follow, if that's all you did, you would experience 5% of what it has to offer.
I think it's also the first game of its kind with multiplayer. (I could be wrong)
It got 10's from most everyone for reasons other then "almost the same but with improved graphics"
You are : GTA : LCS was the first with multiplayer and Saints Row was the first with online multiplayer .
On topic : its interesting how some developers are going so loudly against casual gamers/games ... though I agree with them I also know that ~ 60% of all who will buy GTAIV will be casual gamers :P