Actually I don't quite understand the uproar unlimited ammo regularly creates. Most shooters (survival and tactical shooters aside) already have unlimited ammo, i.e. they throw so much ammo at you, it might as well be unlimited.
And as a side note, the way ammo is handled now makes games damn predictable. I still remember HL2, where you pretty much knew in advance what's going to happen, just by the ammo that dropped.
therefore i dont liked HL2, and that's why most today's shooters suck, i have to play my 1st playthrough on highest difficulty, because it's around the lowest difficuly in 1995... and then... end of fun... no higher difficulties available...
if there is no thrill to run out of ammo, there's no reason to play it at all... go play Alien vs Predator 1, and see how a FPS can be thrilling if you dont have billions of bullets lying around...