Well, my reply to that article is "so what?" as well. Average graphics didn't stop Resistance 1 and 2 from selling, and KZ2, for all it's graphics, is just a pretty standard, run of the mill FPS.
Besides, the graphics do look a bit different because of the different art direction, the vision modes, etc.
It's Halo, it will sell regardless of Metacritic score or whatever.