As others have said, I think exclusives are better because they are then able to take full advantage of the hardware for which they are being made. Very few multiplat games do this, one example being the ps3 port of Oblivion, which took a whole extra year to come out.
If Kameo was designed with both systems in mind, would the textures have looked near as good? No. If MGS4 or Killzone 2 were designed with both systems in mind, would you still have the same crazy amount of effects going on? No.
Look at it this way: You have two pieces of wood. One has a star shaped hole in the middle, and one has a square shaped hole in the middle. Both holes have the same area, but are entirely different shapes. Now let's say you have another piece of wood that you must fit into one or both of the wholes. If you make it star shaped, it will fill up the first hole perfectly. If you make it square shaped, it would fill up the second hole perfectly, and it would be the same area of that which was star shaped.
However, if you were to try to make it able to fit in both wholes, you would have to cut corners from both shapes, making each far smaller than they could've been.







