If you're rating this game solely on its own without ever playing GTA, then it would be a 6, maybe. Now, after playing the most recent GTA only makes you realize just how much better it was or how much worse Saints Row is. However, I did play it slightly longer then Army of Two (Less then 30 minutes) but you will not get through much of it if you've played and enjoyed GTA.
This game is not GTA it's Saints Row. I think Saints Row is actually a better game. Sure the graphics aren't quite as good in Saints Row but that's the only thing about GTA IV that really stands out. As far as story and game play Saints Row has the edge, it's more fun to play. The only knock on this game is there are a few glitches here and there, it actually froze up on me 3 times during my first 2 to 3 hours into the game. Saints Row will always be compared to GTA because they are both crime sandbox style games and of corse they are comparable by that fact but play them both and you will see that they are in fact very different.