MS having a skewed number of 360's sold in NA compared to WW has proven to be an advantage in terms of selling software. They can afford to create and effectively market a game for a single market.

Over half the 360's in the world are in NA (about 56% last time I checked). So MS create and market games for their biggest audience. Roughly 60% of Gears games sell in NA, 66% of Halo, nearly 70% of Fable. The vast bulk of their biggest game series sales coming from one market.

Besides GT in Europe, Sony's titles generally have more of a worldwide split.  With only 25m hardware units in NA, some series that could be bigger, ala GOW or Uncharted are not able to because of the lower install base and NA is the region these titles would sell best. While Sony's lead in EU has lead to GT selling the most units ever there and about 65% of Fifa games selling on the PS3, the core games Sony are offering just don't sell as well in the region. Out of the 28 Sony games in the OP, 22 of those games sold more copies in NA.

So while I think MS are a more successful publisher, a lot of it is down to install base, and what market/distribution that install base has. The nearly 9 million consoles Sony has in Japan really does nothing for most of their exclusives, unless they're japanese centric, but Sony has had it's eyes set on the west this entire generation.