Storylines are pretty insignificant in games with bodycounts this high, anyway. If you've done it in a third-person shooter before, you'll be doing it here- though in inferior fashion. Hostages don't live long enough to be useful, and usually talk after they die. Cover rarely stops enemy fire. Disarms are useless, because you can't get near anyone long enough to pull them off. Your backup does well in a firefight; in more puzzle-oriented situations, however, you sometimes have to literally push them into position. Robbing corpses is one of the few new mechanics- but we'll wait until the sequel, when 50 will no doubt pee on his deceased foes' bodies.
Of course, the game can barely do run-and-gun shooting right, so expecting these features to be well implemented is extremely wishful thinking. Enemies are dead-eyed snipers with ninja speed. You, on the other hand, have no lock-on targeting and moves like you just hit the pipe. If only 50 Cent was bulletproof like the name says. He's not, and you'll die time and time again.